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Question 1

Ascariasis

Answer 1

present with intestinal symptoms and eosinophilia, but more often has a lung phase with nonproductive cough followed by an asymptomatic intestinal phase.? Ascariasis can also present with the worms obstructing the small bowel or bile ducts.

Question 2

Brown recluse spider

Answer 2

the upper arm, thorax, or inner thighs.? Bites are characterized by a red plaque or papule with central clearing; some patients develop a necrotic eschar.

Question 3

Infective endocarditis

Answer 3

fever, cardiac murmur, and embolic phenomenon (eg, subungual splinter hemorrhages).? Although this patient’s drug abuse history can suggest endocarditis,

Question 4

Kaposi sarcoma

Answer 4

This patient with a history of injection drug use presents with clusters of violaceous skin papules indicating likely Kaposi sarcoma (KS), an AIDS-defining illness.? KS is an endothelial malignancy triggered by the reactivation of human herpesvirus 8 (HHV8).

HIV-associated KS is typically marked by the development of papular cutaneous lesions that may become confluent.?

The lesions are violaceous, pink, red, or brown due to an abundance of erythrocytes within the tumor vasculature and tissue.? Pruritus, pain, and skin necrosis are rare.? Obstruction of draining lymphatic channels can cause distal lymphedema (eg, lower extremity swelling).? Visceral lesions in the lungs and gastrointestinal tract may be life-threatening.

Because the tumor arises due to unchecked HHV8 replication in the setting of profound immunosuppression (eg, low CD4, high viral load), first-line treatment is antiretroviral therapy (ART).?

Question 5

Streptococcus pneumoniae

Answer 5

HIV are at increased risk for community-acquired pneumonia (CAP), particularly in the setting of advanced disease (CD4 count <200/mm3).? Streptococcus pneumoniae causes the majority of cases, likely due to increased rates of colonization and impaired immunity against encapsulated bacteria.

“Rusty sputum” is classic for pneumococcal pneumonia but may not always be present.?

Pneumococcal vaccination is recommended for all patients with HIV to reduce the risk of invasive S pneumoniae disease.

usually causes respiratory tract infections (eg, pneumonia), meningitis, or bacteremia.

Question 6

Actinomyces

Answer 6

Actinomyces causes abscesses primarily at the head and neck with characteristic granular yellow pus (“sulfur granules”).? It can also cause indolent pulmonary disease.

Penicillin G is the treatment of choice for Actinomyces, another filamentous gram-positive bacterium.?
Actinomyces is anaerobic, not aerobic; Actinomyces is not acid-fast; and sulfur granules may be found with Actinomyces infection.

Actinomyces is an anaerobic bacterium of the oral cavity that may cause invasive disease in patients with dental infections or trauma (eg, tooth extraction).? Risk of infection is increased in those with poorly functioning immunity due to underlying immunosuppression, diabetes mellitus, or malnutrition.

Patients typically develop a chronic, slow-growing, nontender, indurated mass that eventually forms multiple sinus tracts to the skin.? A pathognomonic feature is the presence of purulent discharge with “sulfur granules”

penicillin

TB resembles Actinomyces on Gram stain, but TB is usually acid-fast (unlike Actinomyces).

Question 7

acute bacterial meningitis

Answer 7

• This patient’s presentation of fever, headache, nuchal rigidity, vomiting, and altered mental status is consistent with acute bacterial meningitis.? Evaluation of bacterial meningitis includes blood cultures and lumbar puncture (LP).? A head CT scan should be performed prior to LP

Cefepime is a fourth-generation cephalosporin that covers most of the major organisms of bacterial meningitis (eg, Streptococcus pneumoniae, Neisseria meningitidis, group B streptococci, Haemophilus influenzae) as well as Pseudomonas aeruginosa.? Vancomycin provides coverage against cephalosporin-resistant pneumococci, and ampicillin covers Listeria monocytogenes.?

?-Age 2-50: Streptococcus pneumoniae, Neisseria meningitidis
-Age >50: S pneumoniae, N meningitidis, Listeria
-Immunocompromised: S pneumoniae, N meningitidis, Listeria,gram-negative rods

Question 8

Acute giardiasis

Answer 8

can present with diarrhea (can be steatorrhea), flatulence, abdominal cramps, weight loss, and nausea.

Question 9

Acute hepatitis A infection

Answer 9

fever, malaise, jaundice, and hepatomegaly, particularly in patients who have recently traveled to developing countries.?

Question 10

Acute HIV

Answer 10

Acute HIV may cause mononucleosis-like symptoms (eg, fever, fatigue, sore throat, painless lymphadenopathy), a generalized rash, and painful mucocutaneous ulceration (shallow, sharply demarcated, with a white base).?

Mononucleosis-like syndrome?(eg, fever,?lymphadenopathy, sore throat, arthralgias)
Generalized macular rash
Gastrointestinal symptoms

This patient’s subacute gastrointestinal symptoms (eg, diarrhea, nausea, cramps), systemic manifestations (eg, fever, weight loss, night sweats, arthralgias), lymphadenopathy, and transient rash should raise suspicion for acute HIV infection.

Two notable clues (not always present) are painful oral ulcerations and/or oval, pink/red macular lesions

HIV infection often causes a mononucleosis-like syndrome consisting of fever, night sweats, lymphadenopathy, arthralgias, and diarrhea.? Important diagnostic clues include oral ulcerations

Acute HIV infection also causes fever, malaise, and generalized lymphadenopathy, and testing should be performed in this patient.? However, adenopathy in acute HIV is nontender

constitutional symptoms and maculopapular rash on the trunk, neck, and face, not the palms/soles.? Most patients also have diffuse lymphadenopathy, sore throat, and (often) mucocutaneous ulcers.?

Question 11

Acute lymphoblastic leukemia

Answer 11

present with fever, fatigue, lymphadenopathy, splenomegaly, and lymphocytosis.?
however, bone marrow failure would cause a low, rather than an elevated, reticulocyte count, as in this patient.?

cute lymphoblastic leukemia usually causes lymphadenopathy and symptoms related to anemia (eg, fatigue), thrombocytopenia (eg, bruising), or neutropenia (eg, infection).? Peripheral smear would show blasts

Question 12

Adenovirus infection

Answer 12

fever, exudative pharyngitis, malaise, and generalized lymphadenopathy

Question 13

Allergic bronchopulmonary aspergillosis

Answer 13

often manifests with the classic triad of fever, pleuritic chest pain, and hemoptysis.? Imaging usually reveals focal lesions (nodules with or without cavitation).? It is often associated with immunosuppression (eg, HIV with CD4 count <50/mm3).?

causes prolonged cough but usually occurs in those with underlying asthma or cystic fibrosis.? In addition, an elevated eosinophil, not lymphocyte, count is seen

Aspergillosis tends to cause nodules and focal infiltrates on chest x-ray (not bilateral interstitial infiltrates)

? Aspergillus may cause pulmonary disease (upper lobe cavitary disease) in immunocompromised patients, but microscopy would show acid-fast negative hyphae
Voriconazole

Question 14

Aspiration pneumonia

Answer 14

cavitary infiltrate and is common in those with alcohol/substance use disorder.? Most cases occur in the lower lobes (particularly the right lower lobe)

dyspnea, cough productive of foul-smelling sputum, and fever.?

Question 15

Babesiosis

Answer 15

This patient visited a Lyme-endemic area and subsequently developed an annular rash with central clearing, the characteristic lesion of early localized Lyme disease.? Although the rash improved with oral doxycycline, she subsequently developed high fever, anemia, and thrombocytopenia, raising strong suspicion for coinfection with Babesia microti.

Lyme disease is transmitted by the Ixodes scapularis tick during blood feeding.? Because this vector also harbors Anaplasma phagocytophilum and B microti, patients with Lyme disease are often (in 4%-28% of cases) coinfected with multiple pathogens.? Doxycycline is effective against A phagocytophilum but has no activity against B microti.

other signs of babesiosis such as anemia, thrombocytopenia, and/or leukopenia are frequently present.? The diagnosis is confirmed when intraerythrocytic parasites are seen on thin peripheral blood smear.? Treatment with azithromycin and atovaquone is curative.

Question 16

Bartonella henselae (Catscratch disease)

Answer 16

Feline scratch/bite
Flea bite from infected feline

Papule in area of transmission
Prominent, tender regional lymphadenopathy

fastidious, facultative, intracellular, gram-negative coccobacillus.? It is typically transmitted by feline scratch/bite or flea bite.? A papular lesion develops at the site of transmission, and tender regional lymphadenopathy is very prominent.?

catscratch disease is marked by a primary cutaneous lesion (vesicular, erythematous, or papular) at the site of inoculation, patients with this condition have prominent, painful, regional lymphadenopathy,

Bacillary angiomatosis
The organism causes a local dermal infection, spreads to the vascular endothelium, and then attacks red blood cells.? The major manifestations of infection are therefore mostly cutaneous, lymphatic, and endovascular (Cat-scratch disease, bacillary angiomatosis, endocarditis).

Bacillary angiomatosis (BA) is a Bartonella infection seen primarily in patients with HIV with CD4 counts <100/mm3 (CD4-mediated immune response is crucial for control and elimination of the organism).?
Symptoms feature vascular cutaneous lesions that often begin as small reddish/purple papules and evolve into friable pedunculated or nodular lesions.? Constitutional symptoms (eg, fever, malaise, night sweats) are typically present and organ (liver, central nervous system, bone) involvement may occur.

Lesional biopsy with microscopy/histopathology

Doxycycline or erythromycin
Antiretroviral therapy

Question 17

Beh?et syndrome

Answer 17

A pathergy test diagnoses Beh?et syndrome

Beh?et syndrome can cause recurrent genital ulcers but they are usually small, painful, and on the scrotum.? Oral ulcers are also frequently present.

Question 18

Blastomycosis

Answer 18

low-grade fever and violaceous skin lesions with scrapings showing yeast,

affects primarily areas in the Midwest and Upper Midwest regions of the United States, extending into the southern Mississippi Valley.

Primary infection occurs through inhalation, and blastomycosis most often causes a mild to moderate pulmonary infection.? Extrapulmonary disease due to hematogenous spread most commonly affects the skin. ?Bone, prostate, and the central nervous system are also frequently involved.?

Skin lesions of blastomycosis have a characteristic presentation of heaped-up verrucous or nodular lesions with a violaceous hue that may evolve into microabscesses.? Disseminated disease can occur in both immunocompetent and immunocompromised patients, but it is usually more severe in immunocompromised individuals.

Question 19

Candida

Answer 19

colonizes airways and usually does not cause pneumonia.?

Common causes of esophagitis in patients with HIV
Oral thrush usually present
White plaques throughout esophagus
Biopsy: pseudohyphae

The large majority of patients with Candida esophagitis have oral thrush(although lack of thrush does not exclude the diagnosis); most have prominent dysphagia rather than odynophagia

fluconazole

This patient with AIDS has pain with swallowing, substernal burning, and oral thrush (white oral plaques), indicating likely Candida albicans?esophagitis.? Infectious esophagitis is common in patients with advanced AIDS (CD4 count <100/mm3)

Question 20

celiac disease

Answer 20

Tissue transglutaminase antibodies can indicate?celiac disease, which usually presents with weight loss, diarrhea, and malabsorption (eg, steatorrhea).

Question 21

Cellulitis (nonpurulent)

Answer 21

S pyogenes,MSSA, Enterococcus, Haemophilus influenzae, Pseudomonas aeruginosa, and Staphylococcus aureus

Deep dermis & subcutaneous fat
Flat edges with poor demarcation
Indolent (over days) fewer initial systemic symptoms (eg, fever).
Localized (fever later in course)

This patient with erythema, warmth, and swelling of the foot associated with fever and lymphadenopathy has cellulitis, a bacterial infection that involves the deep dermis or subcutaneous fat.? Cellulitis typically occurs when gram-positive skin flora (eg, beta-hemolytic Streptococcus, Staphylococcus aureus) gain access to the subcutaneous space via breaks in the skin (eg, trauma, insect bites, preexisting skin infection).

This patient with chronic interdigital pruritus and skin flaking likely developed cellulitis as a complication of tinea pedis (TP), a dermatophyte infection most commonly caused by Trichophyton rubrum.? TP is one of the most common risk factors for lower extremity cellulitis.? Dermatophytes are generally noninvasive but cause fissuring, erosions, and ulceration that allow bacterial entry into the tissue, particularly when the feet are chronically wet or occluded (eg, by nonbreathable footwear, as in this patient who wears rubber shoes).? Patients with immunosuppression (eg, uncontrolled diabetes) are at particularly high risk of developing both severe TP and secondary cellulitis.

Question 22

Cellulitis (purulent)

Answer 22

MSSA,MRSA

Purulent drainage
Folliculitis: infected hair follicle
Furuncles: folliculitis ? dermis ? abscess
Carbuncle: multiple furuncles

Question 23

Chikungunya virus infection

Answer 23

Caribbean islands and subsequently developed fever, rash, and severe polyarthritis, likely indicating chikungunya, an alphavirus infection transmitted by Aedes mosquitoes.

Manifestations typically include high fever; diffuse maculopapular rash; and symmetric, progressive joint pain that is severe enough to interfere with daily activities.? Joint symptoms begin in the distal small joints of the hands and feet but may affect proximal joints over time.? Transient lymphopenia and thrombocytopenia often occur.

Although fever and rash resolve spontaneously in a few days, up to 70% of patients with chikungunya develop chronic arthralgia/arthritis that lasts months or years

Question 24

Chlamydia psittaci

Answer 24

usually acquired through close contact with birds and causes the abrupt onset of fever, dry cough, and headache.

Psittacosis, caused by Chlamydia psittaci, presents with abrupt-onset cough and headache after exposure to exotic birds

Question 25

Chlamydia trachomatis

Answer 25

Initial small, shallow ulcers (often missed) Then painful & fluctuant adenitis (buboes) Painless Doxycycline is the first-line treatment for lymphogranuloma venereum caused by Chlamydia trachomatis.? Small (2-3 mm), painless genital ulcers appear and then resolve before the development of painful, suppurative inguinal nodes.?

Question 26

Clostridium perfringens

Answer 26

causes gas gangrene and manifests with severe pain, bullae, soft tissue crepitus, and signs of systemic toxicity (including shock and multiorgan failure).?

Question 27

Clostridium tetani

Answer 27

Typical symptoms include tonic contraction and spasm of skeletal muscle (eg, neck stiffness, masseter spasm), which can last up to 4-6 weeks.? The risk for tetanus is greatest in wounds that are deep (eg, puncture wounds) or contain devitalized tissue (eg, burns, crush injuries). Patients (such as this one) with significant or dirty puncture wounds who have received >3 tetanus toxoid doses but have not received revaccination for tetanus within 5 years should be vaccinated.? This patient has not received Tdap in adulthood and should therefore receive a single dose of Tdap at this time Unimmunized, uncertain, or <3 tetanus toxoid doses: Tetanus toxoid-containing vaccine* PLUS TIG history of a puncture wound (eg, splinter) approximately 1 week prior to symptom onset that leads to inoculation with Clostridium tetani spores.? Tetanus toxin travels through lower motor neurons to the CNS, where it inactivates inhibitory interneurons.? Common manifestations include masseter muscle spasm (lockjaw [trismus]), muscle pain and stiffness, and difficulty swallowing. Tetanus is a clinical diagnosis.

Question 28

Coccidioidomycosis

Answer 28

Coccidioidomycosis is a fungal infection endemic to the southwestern United States; it often manifests as CAP with hilar lymphadenopathy. predominantly pulmonary infections ("valley fever").? It has been reported in a wide geographic distribution but is found primarily in the desert Southwest and Central Valley of California. symptomatic infection is often marked by subacute pulmonary symptoms, chest x-ray usually reveals a unilateral (not bilateral) infiltrate with ipsilateral hilar lymphadenopathy.? Tissue biopsy would show spherules with endospores (not yeasts). Symptoms may be subclinical, but many patients (>50%) develop community-acquired pneumonia (CAP) (fever, chest pain, productive cough, lobar infiltrate) often accompanied by arthralgias, erythema nodosum, or erythema multiforme.? Confirmation primarily relies on serologic testing, but cultures are often sent.? Most patients who are otherwise healthy and have mild or moderate disease do not need antifungal treatment and can have regular follow-up to ensure resolution.? However, patients with severe disease or certain risk factors (eg, HIV, immunosuppressive medications, diabetes mellitus) are much more likely to develop dissemination (bones, central nervous system, skin); these patients require antifungal treatment.

Question 29

condylomata acuminata

Answer 29

Podophyllotoxin and imiquimod are topical medications used to treat condylomata acuminata, genital warts caused by certain serotypes of human papillomavirus. skin-colored verrucous and filiform papules in the anal/perianal area, penile shaft, or vulvovaginal and cervical areas.

Question 30

contact dermatitis

Answer 30

erythematous plaques, often associated with vesicle formation, oozing, or crusting.? Itching is typically intense.?

Question 31

Creutzfeldt-Jakob disease

Answer 31

prion disease that causes personality change, dementia, and (often) myoclonus.

Question 32

Cryptococcus

Answer 32

Cryptococcus typically causes patchy infiltrates or nodular lesions Cryptococcal meningoencephalitis The patient presents with fevers, headaches, and signs of elevated intracranial pressure (eg, vomiting, papilledema).? In immunocompromised patients with HIV, this is most consistent with cryptococcal meningitis, typically seen in patients with CD4 counts <100/mm3.? Cryptococcus neoformans is an invasive fungus acquired by the inhalation of spores that primarily causes pulmonary disease cryptococcal antigen testing of cerebrospinal fluid (CSF).? CSF India Ink stain or culture on Sabouraud agar may also identify the organism.? Other features include an elevated opening pressure, low glucose, high protein, and a lymphocytic pleocytosis (although white cells may be reduced in HIV patients) Neuroimaging is performed to exclude mass lesions, although C neoformans infection rarely causes mass lesions in patients with HIV. ? Initial: amphotericin B with flucytosine Maintenance: fluconazole

Question 33

cryptosporidiosis

Answer 33

CD4<180/mm3 Severe watery diarrhea Low-grade fever Weight loss In this patient with a recent CD4 count of 94/mm3, severe watery diarrhea, weight loss, and low grade fevers, cryptosporidiosis is the most likely diagnosis. The pathogen is usually self-limited in immunocompetent hosts, but it may cause severe chronic infection in patients with AIDS (particularly those with CD4 counts <180/mm3).? Stool examination with modified acid-fast stain reveals cryptosporidial oocytes The mainstay of treatment is supportive care and antiretroviral therapy because infection often persists until CD4 counts improve.

Question 34

Cutaneous larva migrans

Answer 34

a creeping cutaneous eruption caused by dog (Ancylostoma caninum) or cat (A braziliense) hookworm larvae.? Most infections are acquired from walking barefoot on contaminated sand (beaches) or soil.? Humans are incidental hosts, and larvae are typically unable to penetrate the dermal basement membrane.? As a result, cutaneous infection without deeper penetration is the norm. symptoms usually start with a pruritic, erythematous papule at the site of larvae penetration (which may go unnoticed).? Within a few days, patients develop symptoms related to larvae migration: intensely pruritic, serpiginous, reddish-brown cutaneous tracks.? Hookworm larvae may cause a papular lesion at the site of entry (usually the lower extremity) and proximal, intensely pruritic, reddish-brown tracks from larval migration.

Question 35

Cytomegalovirus

Answer 35

CD4<50/mm3 Frequent, small-volume diarrhea Hematochezia Abdominal pain Low-grade fever Weight loss Cytomegalovirus (CMV) is a common cause of colitis, esophagitis, or retinitis in patients with AIDS.? However, colonic symptoms typically include frequent, small volume stools that are often bloody Common causes of esophagitis in patients with HIV Large, linear ulcers in distal esophagus Biopsy: intranuclear/intracytoplasmic inclusions CMV esophagitis is generally marked by large, linear ulcers in the distal esophagus and biopsy evidence of intracytoplasmic and intranuclear inclusions; IV ganciclovir is the treatment of choice.? Cytomegalovirus typically causes retinitis (eg, floaters, blurry vision) in patients with HIV who have CD4 counts <50/mm3.? MRI may show periventricular enhancement CMV may cause retinitis, colitis, pneumonitis, encephalitis, and other organ involvement.

Question 36

Cytomegalovirus

Answer 36

typically causes an asymptomatic initial infection.? However, a minority (<10%) of patients develop a mononucleosis-like initial illness (closely resembling Epstein-Barr virus [EBV] mononucleosis) with several weeks of fever, malaise, fatigue, absolute lymphocytosis with >10% atypical lymphocytes, and mild elevations in aminotransferase levels.? Compared with EBV, CMV mononucleosis usually causes much milder pharyngitis, lymphadenopathy, and splenomegaly (or these symptoms may be absent). negative heterophile antibody testing (monospot), and positive CMV IgM serology.? Men who have sexual encounters with men, such as this patient, have higher rates of CMV seroconversion than the general population and are at increased risk for infection with different CMV strains.

Question 37

Deep venous thrombosis

Answer 37

lower extremity pain, swelling, and occasionally erythema and fever.? However, the swelling and erythema typically involve the posterior leg or calf,

Question 38

Dengue fever

Answer 38

usually presents with fever, headache, retro-orbital pain, rash, and significant myalgia and arthralgias.? Patients can also develop hemorrhagic dengue fever with significant hemorrhage in the skin or nose.?

Question 39

Diphtheria

Answer 39

Diphtheria typically presents with fever, malaise, pharyngitis, and lymphadenopathy.? A gray pseudomembrane may cover the tonsils and oropharynx.

Question 40

Disseminated gonococcus infection

Answer 40

cause rash and joint symptoms (eg, tenosynovitis, polyarthralgia).? However, the rash is marked by a few scattered pustules or vesicopustules, not a diffuse maculopapular rash. Polyarthralgia:? Asymmetric pain in multiple distal and proximal joints. Pustular rash:? Most patients have 2-10 pustular or vesiculopustular lesions on the distal extremities; trunk lesions can also occur.? The palms and soles may or may not be affected. Tenosynovitis:? Patients report pain over the flexor tendons of multiple distal joints (eg, wrists, ankles, fingers, toes) and/or pain with passive range of motion of the joint. Systemic signs of infection (eg, fever, chills, malaise) are frequently present. no urogenital symptoms. Because Neisseria gonorrhoeae grows fastidiously, blood and synovial fluid cultures are frequently negative (fewer than one-third of patients had positive blood cultures in one study); therefore, the diagnosis is usually presumptively established by NAAT of urogenital sites.

Question 41

Entamoeba histolytica

Answer 41

presents with dysentery, which is characterized by abdominal pain, diarrhea, and bloody stools.

Question 42

Entamoeba histolytica infections.

Answer 42

Metronidazole-based combination therapy is used to treat Entamoeba histolytica infections. abdominal pain, fever, diarrhea, and weight loss

Question 43

Erysipelas

Answer 43

Streptococcus pyogenes Superficial dermis & lymphatics Raised, sharply demarcated edges Rapid spread & onset Fever early in course Erysipelas is a skin infection of the upper dermis and superficial lymphatic system most commonly caused by group A?Streptococcus.? Infections take hold in areas of skin disruption, often due to minor trauma, inflammation, concurrent infection, or edema.? Patients rapidly develop systemic symptoms (fever, chills), regional lymphadenitis, and a warm, tender, erythematous rash notable for raised, sharply demarcated borders.?

Question 44

Haemophilus ducreyi

Answer 44

painful genital papule that progressed to an ulcer, suggesting Haemophilus ducreyi (chancroid) infection. erythematous papules that evolve into pustules and then erode into painful ulcers. erythematous base, well-demarcated/undermined borders, and an overlying purulent exudate.? Painful inguinal lymphadenitis is common. treatment with antibiotics (eg, azithromycin) is typically curative. Azithromycin or ceftriaxone may be used to treat a chancroid (caused by Haemophilus ducreyi), which is a painful ulcer with an exudative base that may be accompanied by tender, suppurative lymphadenopathy.

Question 45

Herpangina

Answer 45

high fever, malaise, and throat pain.? Examination of the throat typically shows hyperemic yellow or grayish-white papulovesicles.

Question 46

Herpes simplex encephalitis

Answer 46

acute (not subacute) fever, headache, seizures, focal deficits, and altered mental status.? Imaging typically reveals unilateral temporal lobe?enhancing lesions with mass effect. Cognitive and personality changes, as well as focal neurological deficits and/or seizures, are more common in HSV infection due to the temporal lobe involvement (seen on MRI).? Herpes encephalitis is usually marked by acute constitutional symptoms, focal neurologic deficits, and/or seizure.? The herpes rash is vesicular, Lumbar puncture usually reveals significant red blood cells in the cerebrospinal fluid.

Question 47

Herpes simplex virus

Answer 47

Pustules, vesicles, or small ulcers on erythematous base Tender lymphadenopathy Systemic symptoms common Herpes simplex lesions are painful and vesicular Common causes of esophagitis in patients with HIV Orolabial lesions usually present Vesicular or ulcerative round/ovoid lesions ("volcano-like") Biopsy: multinucleated giant cells HSV esophagitis is usually marked by endoscopic evidence of small, round-oval, volcano-like esophageal lesions and multinucleated giant cells/intranuclear inclusions on biopsy; acyclovir/valacyclovir is the treatment of choice painful vesicular lesions on an erythematous base,

Question 48

Histoplasma capsulatum,

Answer 48

a soil-based fungus with a wide distribution found primarily in the Mississippi and Ohio River valleys.? It usually causes an asymptomatic or mild pulmonary infection.? Immunocompromised patients with disseminated disease may develop papular, crusting skin lesions, but disseminated infection is rare in immunocompetent patients. a subacute granulomatous pneumonia with yeasts on tissue biopsy.? Although similar findings are seen with Candida pneumonia or blastomycosis, this patient's history of recent cave exploring suggests infection with Histoplasma capsulatum, a dimorphic fungus endemic to temperate areas of the United States, Asia, Africa, and South/Central America. most readily in soil contaminated with bat or bird droppings, patients often have a history of vocational (eg, chicken farming) or recreational (eg, cave exploring) activities that increase risk of exposure. Manifestations usually begin 2-4 weeks after exposure with subacute fever, chills, malaise, headache, myalgia, CP, and dry cough.? Chest x-ray typically reveals mediastinal or hilar lymphadenopathy (LAD) with focal, reticulonodular, or miliary infiltrates (depending on the degree of exposure).? Diagnosis is usually made with Histoplasma antigen testing of the urine or blood.? tissue diagnosis, which often reveals granulomas with narrow-based budding yeasts. Most cases resolve completely over weeks without intervention.? For those with moderate or severe disease, oral itraconazole or intravenous liposomal amphotericin B can be administered.

Question 49

HIV-associated dementia

Answer 49

cause behavioral and personality changes in those not on antiretroviral therapy.? However, brain imaging with contrast usually shows diffuse brain atrophy, ventricular enlargement, and reduced attenuation of white matter structures.

Question 50

Hodgkin lymphoma

Answer 50

Hodgkin lymphoma may present with asymptomatic lymphadenopathy, sometimes accompanied by prolonged B symptoms (eg, fever, weight loss, night sweats).

Question 51

Human monocytic ehrlichiosis

Answer 51

Transmitted by tick vector (Lone Star tick) Seen in southeastern & south central United States Flu-like illness (high fever, headache, myalgias, chills) Neurologic symptoms (confusion) Rash (<30% in adults) is uncommon ("Rocky Mountain spotted fever without the spots") Ehrlichiosis is characterized by an acute febrile illness with malaise and altered mental status.? Ehrlichiosis is not often associated with a rash (<30% in adults) and is described as "Rocky Mountain spotted fever (RMSF) without the spots."? Neurologic symptoms may include confusion, mental status changes, clonus, and neck stiffness.? Laboratory studies often show leukopenia and/or thrombocytopenia, along with elevated aminotransferases and lactate dehydrogenase. Intracytoplasmic morulae in monocytes PCR testing for Ehrlichia chaffeensis/E ewingii Empiric doxycycline while awaiting confirmatory testing

Question 52

Infectious mononucleosis

Answer 52

+ Tonsillitis/pharyngitis ? exudates ? Hepatosplenomegaly fatigue, malaise, sore throat, fever, and lymphadenopathy.? Splenomegaly and, less commonly, hepatomegaly are also seen. resents with prolonged fever, malaise, and sore throat.? Physical findings include enlarged, erythematous tonsils with exudates; splenomegaly; and lymphadenopathy Elevated transaminases are also seen in most patients due to mild, transient hepatitis. In addition, some patients develop autoimmune hemolytic anemia and thrombocytopenia, rare complications of infectious mononucleosis?due to cross-reactivity of EBV-induced antibodies against red blood cells and platelets.? In particular, IgM cold agglutinin antibodies cause complement-mediated destruction of red blood cells.? This hemolysis, which can occur 2-3 weeks after the onset of EBV symptoms, may lead to jaundice, elevated bilirubin, and increased reticulocyte count, as seen in this patient. leukocytosis and atypical lymphocytes The heterophile antibody (Monospot) test is specific for EBV and detects EBV antibodies that agglutinate to horse red blood cells.? However, results may be negative early in the course of illness, especially during the first week of symptoms (25% false-negative

Question 53

Influenza virus

Answer 53

fever, fatigue, myalgia, pharyngitis, and lymphadenopathy and occurs during the winter months abruptly develop systemic (fever, malaise, myalgias, headache) and upper/lower respiratory (rhinorrhea, sore throat, nonproductive cough) symptoms.? Physical and laboratory examinations are often normal but may show pharyngeal erythema (without exudates) and mild alterations in leukocyte count (low early, high later).? Most patients recover spontaneously and completely within 1 week of symptom onset.? However, patients with advanced age (>65) and chronic medical illness (eg, coronary artery disease, diabetes mellitus) are far more likely to develop complications. Pneumonia is the most common complication of influenza and is the result of either secondary bacterial infection (eg, Streptococcus pneumoniae) or direct viral attack (influenza pneumonia).? Patients with primary influenza pneumonia typically have an acute worsening of symptoms (dyspnea, cough), leukocytosis (although <15,000/mm3), hypoxia, and bilateral, diffuse interstitial infiltrates on chest x-ray.? Hospitalization with supplemental oxygen support and antiviral (eg, oseltamivir) treatment is usually required Influenza may also cause complications in the muscle (myositis, rhabdomyolysis), heart (myocarditis, pericarditis), and central nervous system (encephalitis, transverse myelitis). Streptococcus pneumoniae, Staphylococcus aureus, and (less commonly) Pseudomonas aeruginosa can cause secondary bacterial pneumonia in patients with influenza.? Patients with these infections have high fever, significant leukocytosis (>15,000/mm3), and lobar infiltrates on chest x-ray.?

Question 54

INH hepatotoxicity

Answer 54

has been associated with hepatotoxicity, which can manifest as a mild INH hepatotoxicity or severe INH hepatitis. Severe INH hepatitis presents with clinical manifestations similar to those seen with viral hepatitis (eg, fatigue, nausea, flu-like symptoms, jaundice, aminotransferases >10 times upper limit of normal). In contrast, ~10%-20% of patients taking INH will experience mild, subclinical hepatic injury (mild INH hepatotoxicity) demonstrated only by minor elevations in serum aminotransferases. The prognosis is excellent in these patients and the condition is self-limited, allowing for INH therapy to be maintained with close follow-up. Because the patient in this question is relatively young and otherwise asymptomatic, she can continue taking INH as long as her liver function tests are regularly monitored and remain only mildly elevated.

Question 55

innocent "flow" murmur

Answer 55

innocent "flow" murmur due to hyperdynamic circulation from fever.

Question 56

Jarisch-Herxheimer reaction

Answer 56

Patients with Lyme disease can occasionally develop the Jarisch-Herxheimer reaction following antibiotic initiation.? This reaction (likely reflecting cytokine and immune complex release from killed spirochetes) often causes high fever and worsened systemic symptoms

Question 57

Klebsiella

Answer 57

Klebsiella and Pseudomonas primarily cause nosocomial pneumonia.? Although Klebsiella can cause aspiration pneumonia, this patient has no clear features (eg, impaired consciousness, dysphagia) that put her at risk for aspirating. including hospital-acquired pneumonia. Klebsiella pneumoniae and mixed anaerobes often cause pulmonary infections in those at risk for aspiration (eg, alcoholism).? Symptoms of putrid sputum and infiltrates in the dependent pulmonary lobes (right lower, right middle) are common

Question 58

Legionella

Answer 58

high fever (>39 C [102.2 F]), pulmonary symptoms (dyspnea, cough), and gastrointestinal symptoms (nausea, vomiting, diarrhea).? Erythromycin atypical community-acquired pneumonia with central nervous system (confusion) and gastrointestinal (abdominal pain, diarrhea, hepatitis) features.? The primary environmental source of Legionella pneumophila is water Recent travel (especially cruise or hotel stay) within the previous 2 weeks Contaminated potable water in hospitals/nursing homes Bradycardia relative to high fever Neurologic symptoms (especially confusion) Gastrointestinal symptoms (especially diarrhea) entral nervous system and gastrointestinal involvement to fulminant disease with multi-organ failure.? Relative bradycardia (despite high fever) is a classic association; hyponatremia and mild hepatitis, as in this patient, are frequently seen.? Legionella is an intracellular gram-negative rod, so sputum Gram stain may show neutrophils but no organisms.? The diagnosis can be made by culture, generally from bronchoscopy.? However, Legionella is difficult to recover even when selective media (buffered charcoal yeast extract) are used.? Urine antigen testing is rapidly available, highly specific, and the most common method to confirm the diagnosis macrolide or fluoroquinolone.

Question 59

Lung adenocarcinoma

Answer 59

fever, weight loss, dyspnea, and pleural effusion, as seen in this patient.? However, lung cancer usually metastasizes to the liver, bone, brain, and adrenal glands.?

Question 60

Lyme disease

Answer 60

Early localized Lyme disease is treated with oral doxycycline or amoxicillin. Ceftriaxone is used for severe complications of Lyme disease such as meningitis and carditis.? Ixodes scapularis, the tick that carries Borrelia burgdorferi, is not commonly found in the southern United States.? The majority (80%) of patients with early localized (primary) Lyme disease (within days of the tick bite) have the classic erythema migrans rash with or without constitutional symptoms. prominent neurologic (eg, encephalitis, cranial nerve palsy, radiculopathy) or cardiac (eg, heart block, pericarditis) manifestations of early disseminated (secondary) Lyme disease.?

Question 61

lymphoma

Answer 61

fever, night sweats, weight loss, and nontender lymphadenopathy Hodgkin lymphoma can present with fever, chills, and weight loss.? Lymphoma can also be associated with splenomegaly

Question 62

malaria

Answer 62

may present with fever, jaundice, hepatosplenomegaly, and anemia in a patient who has recently traveled to a tropical country.? However, malaria causes cyclic fevers fever, chills, and fatigue; anemia, thrombocytopenia, and jaundice are also common

Question 63

Microsporidium/Isosporidium

Answer 63

CD4<100/mm3 Watery diarrhea Crampy abdominal pain Weight loss Fever is rare

Question 64

Mycobacterium

Answer 64

Isoniazid-based combination therapy is the mainstay of Mycobacterium

Question 65

Mycobacterium avium complex

Answer 65

Patients with advanced AIDS (CD4 <50/mm3) Fever & weight loss Abdominal pain & diarrhea LAD & (often) hepatosplenomegaly ? Alkaline phosphatase Blood/lymph node culture ? nontuberculous mycobacteria Patients with AIDS who have CD4 counts <50/mm3 are at greatest risk.? Manifestations include nonspecific systemic symptoms (eg, fever, cough, abdominal pain, diarrhea, night sweats, weight loss), lymphadenopathy, and an elevated alkaline phosphatase level (reflecting hepatic involvement).? Hepatosplenomegaly can also occur. Diagnosis is typically made with blood culture or bone marrow aspirate; treatment with macrolide-based combination therapy is curative, but antiretroviral therapy should be initiated to prevent future infection. First-line treatment includes a macrolide (eg, clarithromycin, azithromycin) combined with ethambutol.? Disseminated MAC often manifests with constitutional (high fever, night sweats, fatigue, malaise, weight loss) and gastrointestinal (diarrhea, abdominal pain) symptoms.?

Question 66

Mycobacterium avium complex

Answer 66

CD4 <50/mm3 Watery diarrhea High fever (>39 C [102.2 F]) Weight loss

Question 67

Mycoplasma pneumoniae

Answer 67

not acutely) with headache, malaise, nonproductive cough, and low-grade fever. Erythromycin

Question 68

Naegleria fowleri

Answer 68

fresh-water amoeba that may cause acute meningoencephalitis (fever, headache, vomiting, altered mental status, seizures) with a mortality rate of approximately 99%

Question 69

Neisseria gonorrhoeae

Answer 69

cervicitis or urethritis

Question 70

Nocardia

Answer 70

Actinomyces and Nocardia are Gram-positive rods (and Nocardia is also weakly acid-fast).? Nocardia often presents as a subacute pneumonia that mimics tuberculosis infection.? The majority of patients are immunocompromised. may cause pulmonary or cutaneous infection; however, patients are almost always immunocompromised (eg, HIV, glucocorticoid therapy, diabetes mellitus), and infection frequently involves the central nervous system.? This immunocompromised patient has systemic symptoms, lung nodules, and brain abscess (causing seizures), and the cultures grow gram-positive, partially acid-fast, filamentous, branching rods.? Nocardiosis classically affects immunocompromised hosts and may initially be confused with tuberculosis. alveolar infiltrates and nodules, often with cavitation.? Nocardia is an aerobic bacteria found in soil that may inoculate humans via inhalation (most common) or cutaneous penetration (often while gardening). Pulmonary nocardiosis is the most common manifestation and may present alone or with disseminated disease (eg, skin, central nervous system).? Symptoms arise with varying chronicity but often include fever, weight loss, malaise, dyspnea, cough, and pleurisy.? Imaging typically reveals nodular or cavitary lesions in the upper lobes, which may be confused with malignancy or tuberculosis. Gram stain shows filamentous gram-positive rods that are weakly acid-fast (unlike Mycobacterium tuberculosis?[Choice E], which is strongly acid-fast) Trimethoprim-sulfamethoxazole

Question 71

Occupational HIV postexposure prophylaxis

Answer 71

Treatment with ?3-drug regimen recommended: Two nucleotide/nucleoside reverse transcriptase inhibitors (eg, tenofovir, emtricitabine) PLUS: Integrase strand transfer inhibitor (eg, raltegravir), protease inhibitor, or nonnucleoside reverse transcriptase inhibitor If the HIV status of the source patient is unknown but the patient has risk factors for HIV, PEP should be initiated while awaiting results of HIV testing. Initiate urgently, preferably in the first few hours Continue for 4 weeks

Question 72

Parvovirus B19

Answer 72

fever, rash, and arthritis.? However, the rash is usually on the malar surface and is then followed by a lace-like rash on the trunk and extremities.? Parvovirus B19 can cause a transient viral illness with nonspecific flu-like symptoms (eg, malaise, myalgia, fever), arthralgia, and/or rash (eg, circumoral pallor, reticulated/lace-like).

Question 73

Pasteurella multocida

Answer 73

small gram-negative coccobacillus transmitted to humans most often via dog/cat bite or cat scratch.? Although the infection frequently causes cellulitis and may cause lymphangitis, it tends to progress very rapidly (eg, within 24 hours) and to be life-threatening.?

Question 74

Pertussis

Answer 74

This patient has a prolonged cough and sudden-onset, posttussive, focal rib pain consistent with a rib fracture.? Along with lymphocytosis and absence of fever or abnormal lung findings, this presentation raises suspicion for infection with Bordetella pertussis, a highly contagious, gram-negative bacterium transmitted by respiratory droplets. Catarrhal phase (weeks 1-2):? Prodromal symptoms (eg, malaise, cough, rhinitis) are mild and nonspecific, as seen in this patient.? Fever is absent or low-grade. Paroxysmal phase (weeks 2-8):? Damage to the ciliated epithelium causes microaspiration of oral secretions and results in coughing paroxysms.? The classic inspiratory whoop and posttussive emesis are often absent in adults, but cough can be severe and result in rib fractures, hernia, or subconjunctival hemorrhage. Posttussive emesis or syncope can also occur in the paroxysmal stage, Lymphocyte-predominant leukocytosis (toxin-induced), as seen in this patient, is an important diagnostic clue. the diagnosis is clinical.? Nasopharyngeal PCR testing is helpful for providing epidemiologic data or confirming the diagnosis.? Macrolides (eg, azithromycin, clarithromycin) are the first-line treatment and should be initiated based on clinical suspicion without waiting for confirmatory testing. Acquired immunity wanes 5-10 years postvaccination, allowing fully immunized patients to be susceptible to infection, as seen in this patient.

Question 75

Pneumocystis pneumonia

Answer 75

Trimethoprim-dapsone is an alternative treatment regimen for Pneumocystis pneumonia (PCP). -progressive respiratory distress, hypoxia, dry cough, and fever Pneumocystis pneumonia (PCP) is seen primarily in patients with CD4 counts <200/mm3 and manifests with indolent symptoms of dyspnea, nonproductive cough, and (usually) bilateral, diffuse interstitial infiltrates.?

Question 76

primary CNS lymphoma

Answer 76

AIDS-defining illness that occurs much more often in patients with advanced AIDS (compared to the general population), imaging usually reveals a single, well-defined, ring-enhancing lesion with surrounding edema.?

Question 77

Progressive multifocal leukoencephalopathy

Answer 77

This patient with untreated AIDS has progressive neurologic symptoms and imaging evidence of nonenhancing, asymmetric white matter lesions, raising strong suspicion for progressive, multifocal leukoencephalopathy (PML), a life-threatening neurologic disease caused by the reactivation of JC virus. JC virus is usually acquired in childhood and lies dormant in the kidneys and lymphoid tissue; most individuals remain asymptomatic.? However, those with severe immunocompromise (eg, AIDS with CD4 count <200/mm3) are at risk for reactivation.? Reactivated virus spreads to the CNS and lyses oligodendrocytes, causing white matter demyelination. Symptoms include altered mental status, motor deficits, ataxia, and vision abnormalities (eg, diplopia).? Diagnosis requires lumbar puncture with cerebral spinal fluid evidence of JC virus (by polymerase chain reaction) There is no specific treatment for PML, but initiation of antiretroviral therapy can sometimes prevent progression and death JC virus causes progressive multifocal leukoencephalopathy, an opportunistic infection seen in patients with HIV that can be detected on polymerase chain reaction testing of cerebrospinal fluid.? Neuroimaging usually shows patchy areas of white matter consistent with demyelination.

Question 78

Prosthetic joint infection

Answer 78

PJI can be acquired by perioperative contamination of the joint or by extension from an overlying wound infection: Infections due to virulent organisms (eg, Staphylococcus aureus, Pseudomonas aeruginosa) typically present within the first 3 months after surgery Infections due to less virulent organisms (eg, coagulase-negative staphylococci, Propionibacterium species), as in this patient, are likely to have a delayed onset (3-12 months) and present with chronic pain

Question 79

Pseudomonas

Answer 79

Klebsiella and Pseudomonas primarily cause nosocomial pneumonia.? Although Klebsiella can cause aspiration pneumonia, this patient has no clear features (eg, impaired consciousness, dysphagia) that put her at risk for aspirating. Pseudomonas aeruginosa typically causes nosocomial pneumonia.

Question 80

Pseudomonas

Answer 80

external otitis, which is often accompanied by ear pain and discharge, an edematous ear canal, and hearing loss (not seen in this patient).

Question 81

pyelonephritis

Answer 81

dysuria, pyuria, fever, and costovertebral angle tenderness has pyelonephritis. Uncomplicated: Primarily Escherichia coli. =>Oral fluoroquinolone, trimethoprim-sulfamethoxazole Complicated: Diabetes, urinary obstruction/instrumentation, renal failure, immunosuppression, hospital-acquired ? Risk of antibiotic resistance/treatment failure Intravenous fluoroquinolone, aminoglycoside, extended spectrum beta-lactam/cephalosporin Pyelonephritis is a serious infection and usually requires 7?14 (not 3) days of antibiotics. After 48 hours of symptomatic improvement, most hospitalized patients can be transitioned to culture-guided oral antimicrobials. This patient with an Escherichia coli urinary infection sensitive to 2 oral agents can be switched to oral trimethoprim-sulfamethoxazole (a narrower-spectrum antibiotic than ciprofloxacin) and discharged. uncomplicated pyelonephritis usually develop symptoms of cystitis (dysuria, frequency, urgency, suprapubic pain, and/or hematuria) along with flank pain, abdominal or pelvic pain, nausea, vomiting, fever (>38 C), or costovertebral angle tenderness. Patients should have urine culture and receive empiric oral antibiotics against Gram-negative organisms (eg, fluoroquinolone). Hypotensive patients require hospitalization and blood cultures to determine the causative organism, evaluate for bacteremia, and check for drug-resistant organisms.? These patients also need aggressive resuscitation with intravenous fluids and empiric intravenous antibiotics.? maging is typically reserved for patients with persistent clinical symptoms despite 48-72 hours of therapy, history of nephrolithiasis, or unusual urinary findings (eg, gross hematuria, suspicion for urinary obstruction). Complicated pyelonephritis involves progression of the initial pyelonephritis to renal corticomedullary abscess, perinephric abscess, emphysematous pyelonephritis, or papillary necrosis. These patients usually require imaging to evaluate for these complications, urological evaluation, and prompt therapy (medical/surgical).

Question 82

Q fever

Answer 82

a tick-borne illness caused by Coxiella burnetii.? A prolonged, flu-like illness generally develops. C burnetii is a pleomorphic rod, not a coccobacillus.

Question 83

Rabies

Answer 83

Rabies usually manifests with prodromal symptoms (eg, fever, chills, malaise, headache) followed by hydrophobia, pharyngeal spasms, hyperactivity, coma, and death. postexposure prophylaxis (PEP) consists of rabies immunoglobulin plus a series of rabies immunizations. Patients bitten by high-risk wild animals (eg, bats, raccoons, foxes, skunks) should receive PEP if the animal is unavailable for testing.? Because bat bites can go unrecognized, PEP is also recommended following direct exposure to bats (unless the patient is certain a bite or scratch was not inflicted).? In the rare situation that the high-risk wild animal is available for testing, PEP can be withheld until the animal is euthanized and its brain is tested for rabies. Patients bitten by pets in the United States do not require PEP if the animal appears healthy and is available for quarantine (as in this case).? Contagious animals (ie, rabies virus present in saliva) are symptomatic within 5-10 days; therefore, pets can be observed for 10 days for signs of rabies without administering PEP immediately (Choice D).?

Question 84

Rat-bite fever

Answer 84

rare disease marked by a flu-like illness, diffuse maculopapular rash, and arthralgia.?

Question 85

reactivation tuberculosis

Answer 85

This patient with HIV has a chronic cough and a cavitary upper lobe lung lesion, raising strong suspicion for reactivation tuberculosis (TB).? Most healthy patients exposed to TB never develop symptoms due to the generation of granulomas that wall off the bacilli and prevent spread (latent TB). IV is particularly associated with TB reactivation ? weeks of progressive fever, weight loss, and cough; the cough is initially minimally productive and greatest in the morning due to pooling of secretions overnight but eventually becomes more productive, persistent, and, sometimes blood-streaked. preferentially attacks the upper lobes of the lung, where there is high oxygen tensions and slow lymphatic drainage, allowing the organism to accumulate.? Chest imaging typically reveals cavitary lesions Diagnosis requires identification of the organism in sputum samples.?

Question 86

Reactive arthritis

Answer 86

asymmetric oligoarthritis, conjunctivitis, and oral lesions 1-4 weeks after a gastrointestinal or genitourinary tract infection.? Chlamydia trachomatis and Salmonella species can be associated with reactive arthritis following an initial genitourinary or gastrointestinal infection.? Reactive arthritis is characterized by asymmetric oligoarthritis with urethritis/enteritis and conjunctivitis

Question 87

rheumatic fever

Answer 87

sore throat is quite common in young children.? Although rheumatic fever can cause migratory polyarthritis and rash, the rash is subcutaneous nodules or erythema marginatum (evanescent, pinkish rash)

Question 88

RMSF

Answer 88

a maculopapular rash (involving the soles and palms) occurs a few days after the onset of fever. Doxycycline is the first-line treatment. Nonspecific fever, headache, myalgia, arthralgia Macular & petechial rash on wrists/ankles Can develop complications of encephalitis, pulmonary edema, bleeding, shock ? Platelets ? Sodium ? AST & ALT constitutional symptoms, confusion, signs of septic shock (eg, fever, tachycardia, hypotension), petechial rash, and minimal leukocytosis on lumbar puncture raise strong suspicion for Rocky Mountain spotted fever (RMSF), This bacterium attacks vascular endothelial cells, which causes progressive capillary permeability, fluid extravasation, hypovolemia, and poor tissue perfusion. fever, myalgia, nausea, vomiting, headache) that resemble a viral illness.? A maculopapular rash subsequently develops on the wrists and ankles, involves the palms/soles, and progresses centrally.? Over time, increased microvascular injury causes the rash to become petechial, a classic feature of RMSF.? Life-threatening noncardiogenic pulmonary edema (eg, bilateral rales) and shock (eg, hypotension, tachycardia, poor arousal) can occur. reveals thrombocytopenia due to intravascular platelet destruction and hyponatremia (increased ADH due to hypovolemia).? RMSF usually have mild leukocyte elevation (eg, <100/mm3), minimal protein elevation, and normal glucose. empiric doxycycline

Question 89

Secondary bacterial pneumonia

Answer 89

most common complication of influenza and should be suspected in any patient who develops worsening fever and pulmonary symptoms (eg, dyspnea, productive cough) after initial symptomatic improvement.? Patients >65 and with certain comorbid conditions (eg, immunosuppression, lung disease) are at greatest risk.? Streptococcus pneumoniae and Staphylococcus aureus are the 2 most common etiologic organisms. S aureus pneumonia tends to be severe, necrotizing, and rapidly progressive.? Patients often have high fever, hypotension, dyspnea, hemoptysis, and confusion.? Chest x-ray may reveal lobar or multilobar infiltrates with or without cavitation. Patients usually require treatment in the intensive care unit and are often started on multiple broad-spectrum, empiric antibiotics (eg, vancomycin, piperacillin-tazobactam, and levofloxacin).?

Question 90

Secondary syphilis

Answer 90

fever and rash.? However, the rash is usually generalized, symmetric, and maculopapular and typically occurs on the trunk, extremities, palms, and soles. Most patients with secondary syphilis also have palpable lymphadenopathy. Diffuse rash (palms & soles) Lymphadenopathy (epitrochlear) Condyloma latum Oral lesions Hepatitis Secondary syphilis is characterized by systemic symptoms (fever, malaise, sore throat, headache), widespread lymphadenopathy (LAD), grey mucous patches, raised grey genital papules (condylomata lata), and a diffuse maculopapular rash that begins on the trunk, extends to the extremities, and involves the palms and soles.? The presence of epitrochlear LAD is particularly characteristic of secondary syphilis intramuscular penicillin G benzathine

Question 91

Septic emboli

Answer 91

can occur in patients with intravenous drug use (eg, from thrombophlebitis) and cause hemoptysis from pulmonary infarction.? However, most cases are peripheral and multifocal (ie, would be unlikely to cause a single, large cavitary lesion), and patients are acutely

Question 92

solid organ transplantations-associated infections

Answer 92

Patients receiving solid organ transplantations require high-dose immunosuppressive medication to prevent organ rejection.? This results in systemic immunosuppression, which puts them at risk for opportunistic infections, most notably Pneumocystis pneumonia (PCP) and cytomegalovirus (CMV). Oral trimethoprim-sulfamethoxazole (TMP-SMX) is the most effective and well-tolerated medication for PCP prophylaxis. TMP-SMX also has efficacy against most strains of Listeria monocytogenes and Toxoplasma gondii, This patient was on prophylaxis for PCP (trimethoprim-sulfamethoxazole) and CMV (valganciclovir), but both medications were discontinued 2 months ago due to leukopenia.? She now presents with pulmonary symptoms (dyspnea on exertion, dry cough), gastrointestinal symptoms (abdominal pain, diarrhea, hematochezia), pancytopenia, mild hepatitis, and interstitial infiltrates on chest x-ray.? This combination of findings strongly suggests tissue-invasive CMV disease (causing pneumonitis, gastroenteritis, and hepatitis). Treatment involves discontinuing antimetabolite immunosuppression (eg, mycophenolate) and initiating antiviral therapy. Intravenous ganciclovir is used for patients with severe disease (eg, pneumonitis, meningoencephalitis, high viral loads, significant gastrointestinal disease).? Patients with minimal signs and symptoms can take oral valganciclovir. Vaccinations for pneumococci and hepatitis B are typically given prior to transplant to ensure an adequate immune response lso receive prophylaxis with ganciclovir or valganciclovir for cytomegalovirus,

Question 93

splenic abscess

Answer 93

classically causes the triad of fever, leukocytosis, and left upper-quadrant abdominal pain (due to a splenic fluid collection).? Patients can also develop left-sided pleuritic chest pain, left pleural effusion, and splenomegaly.? Risk factors for splenic abscess include infection (eg, infective endocarditis) with hematogenous spread, immunosuppression, IV drug use, trauma, and hemoglobinopathies.? Diagnosis is usually confirmed by CT scan of the abdomen. Common causative organisms are?Staphylococcus, Streptococcus, and Salmonella.? Antibiotics alone for treating splenic abscess have a high mortality (up to 50% in some studies).? As a result, splenectomy is recommended for all patients Patients with preexisting structural cardiac conditions are at increased risk of endocarditis.? There should be strong suspicion for endocarditis in this patient who has mitral valve prolapse therefore, to complete the evaluation for Duke criteria, blood cultures should be obtained and echocardiography should be performed, particularly if blood culture results are positive.

Question 94

Sporotrichosis

Answer 94

Subacute/chronic Papuloulcerative lesion New lesions up lymphatic chain No fever or purulence dimorphic fungus found in soil and decaying plant matter.? Subcutaneous inoculation results in subacute or chronic illness (sporotrichosis).? An ulcerative papule typically forms at the transmission site but is usually nonpainful and does not drain pus.? Similar lesions develop over the proximal lymphatic chain over days or weeks.? Systemic symptoms are rare Pruritus is usually absent or mild. The pustular and ulcerated lesions of sporotrichosis are localized to the site of the wound or associated lymphatic channels. Proximal lesions form along lymphatic chain Distant spread & systemic symptoms are rare Subsequent lesions then typically form along the proximal lymphatic chain (nodular lymphangitis).? However, lymphadenopathy is uncommon, and very few patients experience systemic symptoms or wide-spread dissemination. itraconazole

Question 95

Staphylococcal ecthyma

Answer 95

is a deep form of impetigo that typically begins as a vesicle/pustule on an inflamed area of skin and then converts to an indurated, purulent ulcer.? Lesions are most common on the buttocks, thighs, and legs.? Penile lesions are uncommon,

Question 96

Staphylococcus aureus

Answer 96

Staphylococcus aureus CAP, which usually manifests as rapidly progressive necrotizing pneumonia In addition, although S aureus infective endocarditis can cause septic pulmonary emboli or pneumonia, this patient does not have major risk factors (eg, advanced age, poor dentition, injection drug use) for infective endocarditis;

Question 97

Streptococcal pharyngitis

Answer 97

pharyngitis, fever, and rash

Question 98

Streptococcus agalactiae

Answer 98

peripartum infections

Question 99

Strongyloides stercoralis

Answer 99

cutaneous (pruritus and urticaria), pulmonary, and gastrointestinal symptoms. Strongyloides stercoralis is a helminth that typically causes mild, intermittent skin, gastrointestinal, and pulmonary symptoms over the course of years

Question 100

syphilis

Answer 100

Primary syphilis: indurated margins and a nonexudative base.? Nontreponemal (RPR, VDRL): specific to cardiolipin-cholesterol-lecithin antigen; nontreponemal testing has higher false-negative rates (20%-30%) in patients with primary syphilis, Treponemal (FTA-ABS, TP-EIA) This patient with a new sexual partner developed a single, nonpainful penile ulcer with indurated borders and a clean base, raising strong suspicion for primary syphilis (chancre).? although condom use decreases transmission, it is effective only when covering the active lesion.? In particular, the base of the penile shaft may remain exposed and susceptible to infection despite condom use, as seen in this patient. Primary syphilis typically begins as a small, erythematous papule at the site of inoculation weeks to months after exposure The lesion then develops into the classic chancre, a nonexudative, painless ulcer with a raised edge.? Bilateral inguinal lymphadenopathy, as seen in this patient, is common.? Although spontaneous resolution of the ulcer typically occurs within 6 weeks, systemic spread of infection leads to secondary and/or late syphilis without proper treatment. Penicillin secondary: Diffuse rash (palms & soles) Lymphadenopathy (epitrochlear) Condyloma latum Oral lesions Hepatitis Tertiary: CNS (tabes dorsalis, dementia) Cardiovascular (aortic aneurysm/insufficiency) Cutaneous (gummas)

Question 101

Systemic lupus erythematosus

Answer 101

arthralgias, fever, weight loss, and lymphadenopathy. can cause constitutional symptoms (eg, fever, myalgias), symmetric arthritis (usually hands), and rash.? However, the rash is typically in sun-exposed areas (eg, malar), not diffuse;

Question 102

Taenia solium

Answer 102

Consumption of undercooked, contaminated pork can lead to gastrointestinal infection with the tapeworm Taenia solium.? Most patients are asymptomatic, but some develop nausea, anorexia, or abdominal pain.?T solium eggs may pass via the fecal-oral route, causing cysticercosis. cysts may degenerate over months or years causing inflammation, edema, and clinical illness. Neurocysticercosis typically manifests as an adult-onset seizure.? Less commonly, patients develop signs of increased intracranial pressure (eg, vomiting, headache, papilledema) due to obstruction of cerebral spinal fluid outflow.? Systemic symptoms are usually absent, and laboratory studies are typically normal.? Brain imaging (CT, MRI) usually reveals >1 cystic lesion with surrounding contrast enhancement and edema Cysts at various stages of development (hypodense lesions without enhancement, calcified nodules) are also sometimes found.? Patients are treated with antiepileptics (eg, phenytoin), antiparasitics (eg, albendazole), and corticosteroids (for brain inflammation). Neurocysticercosis tends to cause seizures, and an MRI of the brain usually reveals a mixture of enhancing, nonenhancing, and calcified lesions (depending on the stage of the cyst).?

Question 103

Toxic shock syndrome

Answer 103

caused by Staphylococcus aureus is associated with prolonged tampon use.? It often presents with fever and rash.? Rash is usually diffuse and sunburn-like; in addition, many patients develop rapid-onset hypotension and multiorgan dysfunction.

Question 104

Toxoplasma gondii,

Answer 104

Cats can transmit Toxoplasma gondii, a protozoan that rarely causes symptomatic disease in immunocompetent individuals but may occasionally present with a mononucleosis-like illness (eg, LAD, fever, malaise).? Serum toxoplasma antibody tests for prior exposure to Toxoplasma gondii.? a ring-enhancing mass lesion seen on neuroimaging.

Question 105

toxoplasmosis

Answer 105

Pyrimethamine-based combination therapy is used to treat toxoplasmosis, which usually causes encephalitis in patients with AIDS. Toxoplasmosis is caused by the reactivation of Toxoplasma gondii, an intracellular protozoan that lies dormant in infected individuals and rarely reemerges unless there are significant deficits in cell-mediated immunity.? Toxoplasma encephalitis typically manifests in patients with advanced HIV (CD4 count <100/mm3).? Symptoms include headache, confusion, fever, focal neurologic deficits, and seizures.? Multiple ring-enhancing lesions are usually present on MRI.?positive T gondii?IgG serology, Although this patient's positive Toxoplasma serology indicates previous exposure (which is quite common), it does not indicate reactivated/active disease. Patients with toxoplasmic encephalitis usually develop headaches, focal neurologic deficits, altered mental status, and fever.? Laboratory studies may be normal, but MRI of the brain usually reveals multiple ring-enhancing lesions (with a preference for the basal ganglia).? There is no reliable test for toxoplasmic encephalitis Treatment with several weeks of sulfadiazine and pyrimethamine plus leucovorin (to prevent hematologic side effects) is required

Question 106

trichinellosis

Answer 106

Ingestion of undercooked meat (usually pork) Intestinal stage (within a week of ingestion): Can be asymptomatic or include abdominal pain, nausea, vomiting & diarrhea During the muscle stage, patients may develop local or systemic findings due to larval migration, including fever, subungual splinter hemorrhages, conjunctival and retinal hemorrhages, periorbital edema, and chemosis.? Larvae entering the muscle can cause pain, tenderness, swelling, and weakness (eg, neck, arms, shoulders).? Laboratory studies show eosinophilia (usually >20%), the hallmark of the disease.? Other findings include possible elevated creatine kinase and leukocytosis.? Diagnosis is suspected clinically with the characteristic triad of periorbital edema, myositis, and eosinophilia.? Severe disease can involve the heart, lungs, and central nervous system. Trichinellosis typically presents with gastrointestinal complaints (eg, abdominal pain, nausea, vomiting) followed by the characteristic triad of periorbital edema, myositis, and eosinophilia (hallmark of the disease).? Other findings include fever, subungual splinter hemorrhages, and conjunctival or retinal hemorrhages.

Question 107

tuberculosis,

Answer 107

Patients with HIV are at increased risk of tuberculosis subacute fever, cough, weight loss, and apical pulmonary disease Gastrointestinal tuberculosis most commonly involves the liver, intestine, and peritoneum. Isoniazid (INH) is a bactericidal antibiotic that is particularly effective against replicating Mycobacterium tuberculosis when used in conjunction with other agents such as rifampin, ethambutol, and pyrazinamide.? Interferon-gamma release assay measures lymphocyte response to tuberculous antigens.? An indeterminate result can occur when patients have high background interferon-gamma levels due to ongoing inflammation or concurrent infection; it can also occur when there is minimal response to control mitogens due to lymphocyte suppression from HIV or immunomodulatory medications (eg, glucocorticoids). TST threshold: A TST is considered positive in an HIV-infected individual when induration is ?5 mm at 48-72 hours.? Patients with positive LTBI testing require chest x-ray (infiltrate, lymphadenopathy) and symptom review (night sweats, fevers, cough) to rule out active TB. - ?10 mm: Recent immigrants (<5 years) from TB-endemic areas Injection drug users Residents & employees in high-risk settings (eg, prisons, nursing homes, hospitals, homeless shelters) Mycobacteriology laboratory personnel - ?15 mm: All of the above plus healthy persons Persons with conditions that result in higher risk for TB reactivation LTBI testing is recommended for all patients with newly diagnosed HIV.? Either the tuberculin skin testing (TST) or interferon-gamma release assay (IGRA) can be used, but IGRA is generally preferred due to higher sensitivity/specificity and lower risk for anergy (false-negative result) at low CD4 counts. rifamycin-based regimen (eg, rifapentine plus isoniazid weekly for 3 months) or 9 months of daily isoniazid plus pyridoxine is generally curative. Mycobacterium tuberculosis would appear on microscopy as acid-fast rods that do not Gram stain (as opposed to the gram-positive, partially acid-fast rods of Nocardia).

Question 108

Tularemia

Answer 108

Hunting/skinning wild animals (eg, hares, rabbits) Tick/mosquito bite Bioterrorism weapon Single skin ulcer Regional suppurative lymphadenitis Fever This patient who works as an animal control officer has an ulcerative skin lesion and tender regional lymphadenopathy, raising suspicion for a zoonotic infection.? The presence of intracellular, gram-negative coccobacilli suggests Francisella tularensis.? Most infections occur following contact with wild animals (eg, hares, rabbits, moles) while hunting, trapping, or skinning or due to a bite from a tick or mosquito that recently feed on an infected animal.? Ulceroglandular disease, the most common presentation, is usually marked by a single papule that ulcerates and forms a central eschar and tender regional lymphadenopathy that may suppurate.

Question 109

Typhoid fever

Answer 109

presents in a progressive manner with fever in the 1st week of illness, abdominal pain and salmon-colored rash in the 2nd week, and hepatosplenomegaly with abdominal complications (eg, intestinal bleeding, perforation) during the 3rd week.

Question 110

ulcerative colitis

Answer 110

erythema nodosum/pyoderma gangrenosum).?

Question 111

Urushiol

Answer 111

Urushiol is the irritant component of poison ivy, poison oak, and poison sumac.? Patients often develop intensely pruritic, linear, vesicular (or plaque or bullous) lesions.?

Question 112

Whipple disease

Answer 112

Whipple disease and inflammatory bowel disease can cause abdominal pain, diarrhea, weight loss, and arthralgias Whipple disease is linked with hyperpigmentation,

Question 113

bacillary angiomatosis.

Answer 113

Bright red, firm, friable, exophytic nodules in a patient with HIV are most likely bacillary angiomatosis Bartonella, a Gram-negative bacillus.? Oral erythromycin Typically, the lesions are papules that become plaques or nodules; the color changes from light brown, to pink, to dark violet

Question 114

Molluscum contagiosum

Answer 114

a poxvirus?and is characterized by centrally-umbilicated, dome-shaped papules that are non-pruritic. Molluscum contagiosum is caused by a pox virus and manifests as skin-colored, pearly, papular lesions, often with a dimple in the center.?

Question 115

viral esophagitis

Answer 115

Severe odynophagia (pain with swallowing) as the predominant symptom No dysphagia (difficulty swallowing) No thrush The most commonly implicated viruses in viral esophagitis include herpes simplex virus (HSV) and cytomegalovirus (CMV). The diagnosis is generally made on upper gastrointestinal endoscopy with biopsy

Question 116

Eosinophilic esophagitis

Answer 116

Eosinophilic esophagitis can be seen in patients who have atopic conditions (eg, asthma, seasonal allergies). dysphagia, heartburn, and refractory acid reflux;

Question 117

Gastroesophageal reflux disease (GERD)

Answer 117

typically presents with heartburn, chest pain, and dysphagia.?

Question 118

Medication-related chemical esophagitis ("pill esophagitis

Answer 118

can cause acute odynophagia due to direct effects of a medication on esophageal mucosa.? tetracyclines, bisphosphonates, and nonsteroidal anti-inflammatory drugs

Question 119

Acute lymphatic filariasis

Answer 119

Acute lymphatic filariasis is typically marked by systemic symptoms (fever), painful lymphadenopathy, and lymphangitis.? Chronic symptoms include disfiguring edema.?

Question 120

malignancy

Answer 120

patient with fever, weight loss, and nontender lymphadenopathy.? Tender, mobile nodes are more suggestive of infection than malignancy.

Question 121

streptococcal pharyngitis

Answer 121

fever, pharyngitis, and tender cervical lymphadenopathy.? However, streptococcal pharyngitis is unlikely to cause generalized lymphadenopathy

Question 122

Streptococcus gallolyticus infective endocarditis

Answer 122

fever, and a mitral valve vegetation group D Streptococcus Approximately 60% of patients with S gallolyticus IE have colorectal cancer other colorectal pathologies (eg, inflammatory bowel disease) also increase the risk of S gallolyticus IE. patients should undergo colonoscopy to evaluate for occult malignancy.

Question 123

infective endocarditis

Answer 123

Systemic emboli (cerebral, pulmonary, or splenic infarcts) Janeway lesions: macular, erythematous, nontender lesions on the palms & soles Osler nodes: painful, violaceous nodules seen on the fingertips & toes Roth spots: edematous & hemorrhagic lesions of the retina low-grade fever, and elevated erythrocyte sedimentation rate Although arthralgias and glomerulonephritis (eg, hematuria, proteinuria, dark and cloudy urine) plus subcutaneous, violaceous nodules on the fingers (Osler nodes) is highly suggestive of infective endocarditis (IE). weeks of nonspecific systemic symptoms (eg, fever, weight loss, myalgia, arthralgia, malaise) Direct cardiac injury:? valvular insufficiency and heart failure (eg, dyspnea, cough, edema) Immunologic response:? immune complex?mediated glomerulonephritis (hematuria, red cell casts) or skin manifestations (eg, Osler nodes) Infectious metastasis:? septic emboli (eg, brain, vertebral body, spleen, lung) or mycotic aneurysm Laboratory studies typically show normocytic anemia (eg, anemia of chronic disease) and elevated erythrocyte sedimentation rate (ESR) Duke criteria helps confirm the diagnosis; 3 sets of blood cultures should be obtained to identify the causative microbe, and an echocardiography should be performed to assess valve function and evaluate for vegetations or complications (eg, perivalvular abscess). Staphylococcus epidermidis: Prosthetic valves/Intravascular catheters/ Implanted devices Staphylococcus aureus: + Intravenous drug users Viridans streptococci: Gingival manipulation/Respiratory tract incision or biopsy Enterococci: Nosocomial urinary tract infections Streptococcus gallolyticus: Colon carcinoma/Inflammatory bowel disease a history of mitral valve prolapse (MVP) had a dental extraction and subsequently developed subacute fever, mitral regurgitation, and a mitral valve vegetation, indicating infective endocarditis (IE) subacute, nonspecific systemic signs/symptoms (eg, malaise, weight loss); new cardiac murmur; signs of embolism; bacteremia with a common IE pathogen; and/or evidence of valvular vegetation?(eg, mobile mass) on echocardiography. Viridans streptococci, a group of commensal bacteria in the mouth and upper respiratory tract, are the most likely organisms to cause IE following dental manipulation (eg, tooth extraction) or respiratory mucosa penetration. Enterococcus, a gram-positive organism, is most likely to cause IE following gastrointestinal or genitourinary procedures involving an infected area of mucosa Staphylococcus aureus and coagulase-negative Staphylococcus (eg, S epidermis) are the most common causes of IE following skin and soft tissue procedures in areas of infection (Choices B and C).? These skin commensals are also the most common causes of IE in users of intravenous drugs. This patient's holosystolic murmur at the lower sternum, which increases in intensity with inspiration, is likely due to tricuspid regurgitation.? In addition, arm cellulitis in a young adult with track marks also suggests intravenous drug use (IVDU).? The combination of fever, generalized weakness, tricuspid regurgitation, and IVDU indicates likely right-sided infective endocarditis (IE).? Staphylococcus aureus is the responsible pathogen for more than half of IE cases in IVDU. Empiric therapy in a native valve should cover methicillin-susceptible and -resistant staphylococci, streptococci, and enterococci.? Vancomycin therefore is the most appropriate antibiotic for empiric therapy in these patients due to its broad spectrum of activity. Aqueous penicillin G is the drug of choice in patients with native-valve IE due to penicillin-susceptible Viridans streptococci.? Penicillin G has essentially no staphylococcal coverage.?

Question 124

poststreptococcal glomerulonephritis

Answer 124

Antistreptolysin titer helps diagnose poststreptococcal glomerulonephritis, which is associated with active urine sediment and dark urine.? However, cases are typically preceded by a sore throat or skin infection

Question 125

Rheumatoid arthritis

Answer 125

Rheumatoid arthritis can cause low-grade fever, fatigue, and elevated ESR.? However, multijoint pain, stiffness, and swelling are usually prominent.? Some patients with IE have positive rheumatoid factor, which is thought to be an immunologic phenomenon of infection.

Question 126

meningococcal meningitis

Answer 126

dramatic leukocytosis (eg, >1000/mm3), high protein, and low glucose

Question 127

bacterial aspiration

Answer 127

This patient underwent upper gastrointestinal endoscopy and subsequently developed community acquired pneumonia develop progressive fever, dyspnea, and cough, which may be productive of foul-smelling sputum.? Chest imaging usually shows an infiltrate in a dependent portion of the lung; in the recumbent position, the dependent segments are the superior portions of the lower lobes and the posterior portions of the upper lobes.? Leukocytosis is often present. Peptostreptococcus, Fusobacterium, gram-negative bacilli, Streptococcus pneumoniae, Staphylococcus aureus) amoxicillin-clavulanate, treated with the same agents as community acquired pneumonia. if Empyema or lung abscess present: extend coverage to include anaerobes (eg, ampicillin-sulbactam) Klebsiella pneumonia is more common in those at risk of aspiration (eg, alcoholism, neuromuscular disorders) and usually causes infiltrates in the dependent lobes (eg, right lower lobe) and foul-smelling sputum.

Question 128

Ciprofloxacin

Answer 128

Ciprofloxacin provides excellent gram-negative coverage but has limited efficacy against many upper respiratory gram-positive organisms.

Question 129

doxycycline

Answer 129

covers atypical organisms in patients with community-acquired pneumonia, it does not have broad enough activity against typical aerobic pathogens to be used as monotherapy.

Question 130

Metronidazole

Answer 130

provides coverage of gram-negative anaerobes but does not adequately cover aerobic pathogens

Question 131

Trimethoprim-sulfamethoxazole

Answer 131

is the drug of choice for Pneumocystis pneumonia and is effective against many gram-negative and gram-positive microbes; however, it does not provide broad enough coverage for upper respiratory aerobic organisms to be used as empiric treatment for aspiration pneumonia.

Question 132

Hep B

Answer 132

This patient's test results (positive HBsAg and positive HBeAg) are consistent with acute hepatitis B (HB).? Positive hepatitis Be antigen indicates a higher risk of transmission.? Healthcare workers (HCWs) exposed to blood (ocular, percutaneous, or mucous membrane) from a suspected or known HB patient should be considered for post-exposure prophylaxis.? HCWs with previous HB vaccination and known antibody response usually require no post-exposure prophylaxis HCWs without previous HB vaccination or adequate antibody response to the vaccine should receive the complete HB vaccine series as soon as possible; Unvaccinated HCWs exposed to an HBsAg-positive source patient (as in this case) should also receive the HB immune globulin as soon as possible, preferably within 24 hours. Active hepatitis B (HB) infection typically presents with positive HB surface antigen, positive Be antigen, and absent surface antibody.? Health care workers exposed to blood from HB patients (ocular, mucous membrane, or skin) should receive post-exposure prophylaxis.? Unvaccinated individuals should receive both the HB vaccine and HB immune globulin as soon as possible.

Question 133

HACEK

Answer 133

Ampicillin-sulbactam, it is recommended for penicillin-resistant enterococcus and HACEK organisms once culture sensitivity results are available.

Question 134

methicillin-resistant S?aureus (MRSA) infection

Answer 134

Clindamycin is occasionally used for the treatment of cellulitis due to methicillin-resistant S?aureus (MRSA) infection

Question 135

Bacillus anthracis

Answer 135

sporulating (not branching, filamentous) bacterium that can be inhaled.? Symptoms progress rapidly and include fever, myalgias, dyspnea, hypoxemia, and shock.

Question 136

Bloody diarrhea

Answer 136

most often caused by infectious gastroenteritis due to bacterial pathogens, specifically Shiga toxin?producingEscherichia coli (STEC), Shigella, or Campylobacter; other organisms that often cause watery stools (eg, Salmonella) can occasionally cause bloody stools. STEC transmission typically occurs via consumption of contaminated beef products, ? This patient's lack of fever is typical of infection with STEC The diagnosis can be confirmed with multiplex nucleic acid amplification testing or assay for Shiga toxin in stool; Treatment is generally supportive (eg, aggressive fluid administration), and antibiotics should be avoided due to the increased risk for hemolytic uremic syndrome.

Question 137

Clostridioides difficile

Answer 137

associated diarrhea presents as frequent, foul-smelling loose stools associated with prior antibiotic use or exposure to health care settings.?Manifestations include watery diarrhea (often with mucus or occult blood), abdominal pain, cramping, and leukocytosis.

Question 138

Clostridium perfringens

Answer 138

a common cause of a toxin-mediated, food-borne illness (eg, contaminated, undercooked meat), leading to nonbloody diarrhea and abdominal pain commonly causes food poisoning and gas gangrene.

Question 139

Listeria monocytogenes

Answer 139

a rare cause of gastroenteritis that presents with watery diarrhea, in addition to a self-limited, flu-like illness (eg, fever, muscle/joint aches) lasting <3 days in immunocompetent patients.?

Question 140

Rotavirus

Answer 140

frequent cause of acute gastroenteritis, particularly in unvaccinated children.

Question 141

bacterial meningitis

Answer 141

Streptococcus pneumoniae is the most common cause of community-acquired bacterial meningitis. Illness is usually secondary to hematogenous dissemination (bacteremia) and may occur with or without concurrent pneumococcal pneumonia. Headache Fever (usually >38 C [100.4 F]) Nuchal rigidity Altered mental status Blood cultures are often positive, but diagnosis requires a lumbar puncture.? Cerebrospinal fluid typically shows high opening pressure (>350 mm H2O), low glucose (<40 mg/dL), high protein (>200 mg/dL), and neutrophilic leukocytosis (>1000/mm3).? Urgent treatment is needed Most patients receive a third-generation cephalosporin (eg, ceftriaxone), vancomycin, and dexamethasone (to reduce inflammatory morbidity).? Vancomycin and ceftriaxone are used empirically for bacterial meningitis.? Ampicillin is added for patients age >50 or those who are immunocompromised due to increased risk of Listeria monocytogenes. Other common, less prevalent causes include Neisseria meningitidis (~12%), Hemophilus influenzae, and L monocytogenes.? Hemophilus

Question 142

Fusobacterium

Answer 142

Lemierre syndrome (LS) is a severe life-threatening infection that affects young immunocompetent patients F necrophorum is part of the normal oral flora.? LS usually begins with an oropharyngeal infection, usually tonsillitis, but can also arise as a complication from dental work or mastoiditis.? The bacterium invades the lateral pharyngeal space through the lymphatic system and affects the neurovascular structures, causing internal jugular vein thrombosis and infection. The classic presentation is a prolonged (eg, weeklong) duration of sore throat with high fever, rigors, dysphagia, and neck pain and swelling along the sternocleidomastoid muscle.? Once the internal jugular vein is infected, septic thromboemboli can seed other organs, particularly the lungs, causing respiratory symptoms and leading to nodules on chest x-ray.? LS should be considered in any toxic-appearing patient with respiratory difficulties and significant neck swelling or tenderness in the week following an oropharyngeal infection.

Question 143

Respiratory syncytial virus (RSV

Answer 143

Respiratory syncytial virus (RSV) infection and influenza share many clinical symptoms, but patients with RSV often have wheezing and rarely (<1%) have diffuse, bilateral reticular infiltrates.

Question 144

Naegleria fowleri

Answer 144

Swimming in fresh water contaminated with Naegleria fowleri can lead to acute meningoencephalitis and death.? Symptoms include fever, headache, and altered mental status,

Question 145

travelers' diarrhea

Answer 145

Although bacterial and viral pathogens are the most common causes of travelers' diarrhea, parasitic organisms such as Cryptosporidium parvum, Cyclospora, and Giardia are responsible for most cases of prolonged, profuse, watery diarrhea. C parvum is an intracellular protozoan transmitted via the ingestion of contaminated water (drinking, swimming).?Although a minority of patients remain asymptomatic, most develop mild or profuse watery diarrhea.? Malaise, nausea, crampy abdominal pain, and low-grade fever may also occur. microscopy with specialized stains is usually diagnostic (routine stool ova and parasite testing does not identify C parvum).? Otherwise healthy adults typically have spontaneous resolution of symptoms within 10-14 days; however, patients who are immunocompromised (eg, AIDS) are at risk for severe, chronic disease.

Question 146

Epidemic typhus

Answer 146

louse-borne rickettsial infection associated with the abrupt onset of fever, severe headache, and malaise; a centrifugally-spreading macular or maculopapular rash (typically sparing the palms and soles) develops several days later.