Infectious Disease II Flashcards

1
Q

What is the likely diagnosis in a patient that presents with flu-like symptoms without a rash after being bitten by a tick two weeks ago? Laboratory exam reveals leukopenia, thrombocytopenia, and elevated LFTs.

A

Ehrlichiosis

carried by ticks, including the lone star tick (Amblyomma americanum), in southeastern and south central United States

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2
Q

What is the likely diagnosis in a patient that presents with high-grade fever, cough, diarrhea, confusion, and hyponatremia? CXR reveals a right lower lobar infiltrate.

A

Legionella pneumoniae (Legionnaire’s disease)

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3
Q

What is the likely diagnosis in a patient that presents with multiple, large painful ulcers on the penis with purulent exudate? The patient also has severe inguinal lymphadenopathy.

A

Chancroid (Haemophilus ducreyi infection)

uncommon in the U.S. but outbreaks have occured in those who trade sex for drugs/money

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4
Q

What is the likely diagnosis in a patient that presents with two days of burning pain on the abdomen, followed by development of the rash below?

A

Herpes zoster (shingles)

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5
Q

What is the likely diagnosis in a patient that recently returned from a trip to Kenya and presents with headache, fatigue, and episodic fever?

A

Malaria

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6
Q

What is the likely diagnosis in a patient that recently returned from Mexico and developed abdominal pain and nausea/vomiting, followed by periorbital edema and muscle pain a few days later? Laboratory exam reveals eosinophilia and elevated creatine kinase.

A

Trichinellosis

usually due to ingestion of undercooked pork in endemic areas

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7
Q

What is the likely diagnosis in a patient who recently emigrated from Mexico and presents with fever, RUQ pain, and bloody diarrhea with a subcapsular liver cyst visible on CT?

A

Amebiasis (liver abscess secondary to Entamoeba histolytica)

presence of fever and a subcapsular liver cyst helps differentiate amebiasis from Echinococcus granulosis (afebrile with a hydatid liver cyst)

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8
Q

What is the likely diagnosis in a patient with a recent UTI that presents with fever, back pain, focal tenderness over the L4-L5 vertebrae, and paravertebral muscle spasm?

A

Vertebral osteomyelitis

most likely due to hematogenous spread of the UTI; initial workup includes CBC, blood cultures, ESR/CRP, and plain spinal X-rays

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9
Q

What is the likely diagnosis in a patient with a slow-growing, painless mass in the mandible? The mass recently began draining a purulent discharge with small yellow granules. The patient’s history is significant for a recent tooth extraction.

A

Cervicofacial Actinomyces infection

gram stain often shows filamentous, branching gram-positive rods

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10
Q

What is the likely diagnosis in a patient with HIV and a CD4+ count of 25/mm3 that presents with altered mental status and motor deficits? Brain MRI reveals focal white matter lesions with no enhancement/edema.

A

Progressive multifocal leukoencephalopathy (PML)

reactivation of JC virus primarily occurs in patients with CD4+ count < 200/mm3

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11
Q

What is the likely diagnosis in a patient with pneumonia symptoms, violaceous/verrucous skin lesions, and bone lesions? The patient works as a construction worker in Wisconsin.

A

Blastomycosis

causes pulmonary, skin, and bone manifestatons and dissemination may occur in immunocompetent individuals; endemic to the Great Lakes, Mississippi river, and Ohio River basins (Wisconsin has the highest rate of infection)

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12
Q

What is the likely diagnosis in a patient with poorly controlled diabetes that presents with fever, bloody nasal discharge, and necrosis of the right nasal turbinate/hard palate?

A

Mucormycosis

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13
Q

What is the likely diagnosis in a patient with poorly controlled HIV that develops multiple violaceous papules in the groin region?

A

Kaposi sarcoma (HHV-8 infection)

may require biopsy (lymphocytic infiltrate) to help differentiate from bacillary angiomatosis (neutrophilic infiltrate)

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14
Q

What is the likely diagnosis in a patient with poorly controlled HIV that presents with a two day history of severe pain with swallowing, but no difficulty swallowing? Oral examination is unremarkable.

A

Viral esophagitis

e.g. due to HSV (circular ulcers) or CMV (linear ulcers); Candida esophagitis is associated with oral thrush and mild odynophagia

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15
Q

What is the likely diagnosis in a patient with poorly controlled HIV that presents with headaches, confusion, fever, and mild neurologic deficits?

Brain MRI: several ring-enhancing lesions

A

Toxoplasma encephalitis

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16
Q

What is the likely diagnosis in a patient with poorly controlled HIV that presents with one week of worsening fatigue, headache, and fever? Physical exam reveals bilateral papilledema. Brain MRI is normal.

A

Cryptococcal meningoencephalitis

diagnosis is established by CSF testing for cryptococcal antigen, India ink stain, or culture on Sabouraud agar

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17
Q

What is the likely diagnosis in a patient with recent travel in rural areas of South America that presents after having a generalized tonic clonic seizure? Brain MRI reveals several cystic lesions with surrounding edema.

A

Neurocysticercosis

caused by ingestion of food/water contaminated with Taenia solium (pork tapeworm) eggs

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18
Q

What is the likely diagnosis in a patient with recent travel out of the country that presents with fever, jaundice, and tender hepatomegaly with very elevated LFTs (AST/ALT > 1,000 U/L)?

A

Acute hepatitis A infection

most patients completely recover in 3 - 6 weeks

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19
Q

What is the likely diagnosis in a patient with recent travel to the Caribbean that presents with fever, polyarthralgias, and a diffuse maculopapular skin rash? Laboratory exam reveals leukopenia and thrombocytopenia.

A

Chikungunya fever

presentation is very similar to Dengue fever, however Dengue fever has more pronounced bone pain and the second infection is more severe than the first

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20
Q

What is the likely diagnosis in a patient with recently diagnosed infective endocarditis that now presents with fever and left-sided chest/abdominal pain? CT reveals a left-sided pleural effusion and splenomegaly with a splenic fluid collection.

A

Splenic abscess (secondary to IE)

splenic abscess usually presents with a triad of fever, leukocytosis, and LUQ abdominal pain; treatment is with antibiotics plus splenectomy

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21
Q

What is the likely diagnosis in a patient with suspected infectious mononucleosis that develops anemia and thrombocytopenia two weeks after the onset of IM symptoms?

A

autoimmune hemolytic anemia

due to IgM (cold-agglutinin) antibodies that cross-react with EBV and RBCs/platelets

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22
Q

What is the likely diagnosis in a patient with syphilis that develops fever, headache, myalgia, and a diffuse macular rash on the palms/soles after receiving a dose of IV penicillin G hours ago?

A

Jarisch-Herxheimer reaction

due to rapid lysis of spirochetes; self-limited and resolves spontaneously within 48 hours

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23
Q

What is the likely diagnosis in a sex worker that presents with fever/chills, polyarthalgia, and pustules on the chest and extensor surfaces of the forearms?

A

Disseminated gonococcal infection

the patient is normotensive, has no abnormal heart sounds, and has a rash that spares the palms and soles (helps rule out toxic shock syndrome, infective endocarditis, and secondary syphilis, respectively)

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24
Q

What is the likely diagnosis in a young adult that presents with headache, fatigue, persistent dry cough, and mild sore throat? There is a faint macular rash on the arms/legs and increased interstitial markings on CXR.

A

Mycoplasma pneumoniae infection (atypical pneumonia)

patients may also have mild hemolytic anemia due to cold agglutins; treatment is empiric macrolide or respiratory fluoroquinolone therapy

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25
Q

What is the likely diagnosis in a young adult that presents with two-days of sore throat, enlarged/erythematous tonsils, lymphadenopathy, and splenomegaly? Many variant forms of lymphocytes are seen on peripheral smear despite a negative heterophile antibody test.

A

Infectious mononucleosis

heterophile antibodies may be falsely negative early in the illness; atypical lymphocytes are suggestive of infectious mononucleosis

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26
Q

What is the likely diagnosis in a young adult with grey mucosal patches in the mouth, epitrochlear lymphadenopathy, and a diffuse maculopapular rash?

A

Secondary syphilis

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27
Q

What is the likely diagnosis in a young patient that presents with two days of fever, altered mental status, seizures, and the lumbar puncture findings below?

Opening pressure: normal

Protein: normal

RBCs: high

WBCs: high

Lymphocytes: 90%

A

What is the likely diagnosis in a young patient that presents with two days of fever, altered mental status, seizures, and the lumbar puncture findings below?

Opening pressure: normal

Protein: normal

RBCs: high

WBCs: high

Lymphocytes: 90%

Viral encephalitis (e.g. HSV)

28
Q

What is the likely diagnosis in an adolescent patient that presents with headache, fever, nuchal rigidity, and lower extremity petechiae?

CSF:

Glucose: low

Protein: high

Leukocytes: high, neutrophilic predominance

A

What is the likely diagnosis in an adolescent patient that presents with headache, fever, nuchal rigidity, and lower extremity petechiae?

CSF:

Glucose: low

Protein: high

Leukocytes: high, neutrophilic predominance

Meningococcal meningitis

requires urgent treatment with a third-generation cephalosporin and vancomycin

29
Q

What is the likely diagnosis in an afebrile farmer with RUQ pain and a smooth, round hepatic cyst with septations and eggshell calcifications on ultrasound?

A

Echinococcus granulosus infection

lack of fever and cystic lesion favor echinococcus rather than entamoeba histolytica (febrile with a smooth, cystic subcapsular mass)

30
Q

What is the likely diagnosis in an Army officer in Arizona that presents with pleuritic chest pain, fever, arthralgias, and erythematous, tender nodules on the bilateral shins? CXR shows a right lower lobe infiltrate.

A

Coccidioides immitis infection

causes community-acquired pneumonia symptoms, often with arthralgias and erythema nodosum; endemic to Southwestern U.S.

31
Q

What is the likely diagnosis in an HIV patient that presents with a two-month history of low-grade fever and a productive cough that is worst in the morning (CXR below)?

A

Mycobacterium tuberculosis infection

reactivation TB preferentially infects the lung apices and presents with subacute or chronic symptoms; reactivation is more common in HIV patients

32
Q

What is the likely diagnosis in an HIV patient that presents with fever and altered mental status with encapsulated yeast visualized on CSF fungal stain?

A

Cryptococcal meningoencephalitis

caused by Cryptococcus neoformans, typically in HIV patients with CD4+ count < 100

33
Q

What is the likely diagnosis in an HIV patient with a CD4+ count of 175/mm3 that presents with fever, dry cough, and hypoxia? Laboratory exam reveals elevated LDH and CXR reveals diffuse, bilateral infiltrates.

A

Pneumocystis pneumonia

severe hypoxia and bilateral interstitial infiltrates in an HIV patient with CD4+ < 200/mm3 favors this diagnosis

34
Q

What is the likely diagnosis in an HIV patient with a CD4+ count of 25/mm3 that presents with 3 weeks of fever, night sweats, abdominal pain, diarrhea, and weight loss? CXR, CMV serology, and PPD are all negative.

A

Disseminated Mycobacterium avium complex (MAC) infection

TB and CMV are less likely given the normal CXR, induration, and negative CMV IgG

35
Q

What is the likely diagnosis in an IV drug user with a history of recent incarceration that presents with two months of intermittent fevers, weight loss, fatigue, and non-productive cough (CXR below)?

A

Miliary tuberculosis

most common behavioral risk factor for TB in the United States is substance abuse

36
Q

What is the likely microorganism causing a UTI in a young female with an elevated urine pH and renal calculus on imaging?

A

Proteus mirabilis

Proteus mirabilis is more likely than E. coli given the urine alkalinization and presence of a renal calculus (magnesium ammonium phosphate, a.k.a struvite, stone)

37
Q

What is the likely result of the following serologic tests in a patient naturally immunized against hepatitis B?

HBsAg: […]

HBsAb: […]

HBcAb: […]

A

What is the likely result of the following serologic tests in a patient naturally immunized against hepatitis B?

HBsAg: negative

HBsAb: positive

HBcAb: positive

HBcAb is negative in patients who are vaccinated

38
Q

What is the likely result of the following serologic tests in a patient vaccinated against hepatitis B?

HBsAg: […]

HBsAb: […]

HBcAb: […]

A

What is the likely result of the following serologic tests in a patient vaccinated against hepatitis B?

HBsAg: negative

HBsAb: positive

HBcAb: negative

HBcAb is positive in patients who are naturally immunized

39
Q

What is the likely result of the following serologic tests in a patient with chronic hepatitis B?

HBsAg: […]

HBsAb: […]

HBcAb: […]

A

What is the likely result of the following serologic tests in a patient with chronic hepatitis B?

HBsAg: positive

HBsAb: negative

HBcAb: positive

40
Q

What is the likely underlying infection in a patient with recurrent blisters on sun-exposed areas with fatigue, nausea, and elevated LFTs?

A

Chronic hepatitis C infection

41
Q

What is the most common cause of community-acquired pneumonia in HIV patients?

A

Streptococcus pneumoniae

presents similarly to bacterial CAP in HIV-negative individuals

42
Q

What is the most common manifestation of carditis secondary to Lyme disease?

A

AV block

43
Q

What is the most common microorganism causing infective endocarditis in IV drug users?

A

Staphylococcus aureus

typically involves the tricuspid valve (right-sided)

44
Q

What is the most common source of infection causing Ludwig angina?

A

Infected mandibular molar (dental infection)

45
Q

What is the most common symptom of bacterial endocarditis?

A

Fever

mnemonic: FROM JANE

46
Q

What is the most reliable sign for vertebral osteomyelitis?

A

Tenderness to percussion over the spinous process of the involved vertebrae

fever and leukocytosis are unreliable findings (often absent), though ESR is typically significantly elevated; suspect vertebral osteomyelitis in a young patient with vertebral TTP and a history of IVDA or recent distal site infection (e.g. UTI)

47
Q

What is the next step for confirming the diagnosis in a patient that developed a non-painful ulcer on the shaft of his penis with negative VDRL and HIV tests?

A

Fluorescent treponemal antibody absorption (FTA-ABS)

FTA-ABS has higher sensitivity in patients with primary syphilis compared to non-treponemal tests (see below)

48
Q

What is the next step in management for a healthcare worker following a needle stick injury while drawing blood from an HIV-positive patient with a high viral load?

A

draw blood for HIV serology and start anti-retroviral therapy with 3 drugs immediately

preferred regimen is tenofovir-emtricitabine with raltegravir for 4 weeks

49
Q

What is the next step in management for a patient being treated with RIPE therapy for TB for the past month that develops mild elevations in AST/ALT?

A

Continue with current treatment; monitor LFTs

subclinical hepatotoxicity is common within the first few weeks of isoniazid therapy; it is typically self-limited and resolves without intervention (significant hepatotoxicity warrants switching treatment regimens)

50
Q

What is the next step in management for a patient found to have positive HCV antibodies?

A

Hepatitis C RNA testing

diagnosis must be confirmed as up to half of patients may spontaneously clear the virus

51
Q

What is the next step in management for a patient that develops fever, malaise, splinter hemorrhages, and aortic regurgitation following a dental procedure?

A

Obtain blood cultures

blood cultures should be obtained before initiating antibiotic therapy or obtaining cardiac imaging in patients with suspected infective endocarditis

52
Q

What is the next step in management for a patient that is bitten by a neighbor’s dog? The dog appears healthy but is not vaccinated against rabies.

A

Observe the dog for 10 days for signs of rabies; post-exposure prophylaxis only if dog is symptomatic

post-exposure prophylaxis includes rabies vaccine and rabies immune globulin and protocol depends on the animal involved

53
Q

What is the next step in management for a patient that notices a tick on the leg with surrounding erythema after spending the past day outside?

A

Remove the tick with tweezers and reassure

prophylaxis (e.g. single dose of doxycycline) for Lyme disease is not required if the tick is attached for < 36 hours

54
Q

What is the next step in management for a patient with HIV and a CD4+ count of 85/mm3 that presents with dysphagia and substernal burning? White plaques that are easily removable are present on the palate.

A

Oral fluconazole

if symptoms do not resolve with oral fluconazole, endoscopy is warranted

55
Q

What is the next step in management for a patient with poorly controlled HIV that presents with mild odynophagia/dysphagia?

A

Empiric fluconazole

mild symptoms are most likely due to Candidal esophagitis, even in the absence of thrush; severe symptoms or symptoms refractory to fluconazole warrant endoscopy with biopsy to assess for other causes (e.g. CMV, HSV)

56
Q

What is the next step in management for a patient with pyelonephritis that has clinically resolved after two days of IV ceftriaxone? Urine culture reveals E. coli sensitive to ceftriaxone and TMP-SMX.

A

Switch to oral TMP-SMX

most hospitalized patients can be transitioned to culture-guided oral antibiotics if symptoms are improved at 48 hours

57
Q

What is the next step in management for a patient with suspected ventilator-associated pneumonia with a CXR demonstrating lobar infiltrate?

A

Gram stain/culture of respiratory secretions

should be obtained prior to administering empiric antibiotics

58
Q

What is the next step in management for a patient with suspected vertebral osteomyelitis that has a significantly elevated ESR with normal spinal X-ray?

A

MRI

followed by CT-guided bone biopsy if positive

59
Q

What is the next step in management for an asymptomatic patient that has a 12-mm induration two days after a PPD injection? The patient has no TB risk factors.

A

No additional intervention required

in the US, an induration size of

60
Q

What is the next step in management for an HIV patient who has an 8-mm induration at 48 hours following PPD testing and a normal chest X-ray?

A

Isoniazid and pyridoxine

this patient should be treated for latent TB

61
Q

What is the preferred diagnostic test for Babesiosis?

A

Peripheral blood smear (“Maltese cross”)

treatment typically is atovaquone + azithromycin (quinine + clindamycin may be used for severe infections)

62
Q

What is the preferred treatment for a patient with cervicofacial actinomyces infection?

A

Pencillin

63
Q

What is the preferred treatment for a patient with infective endocarditis secondary to penicillin-sensitive Streptococcus mutans?

A

IV ceftriaxone (preferred) or IV penicillin G for 4 weeks

ceftriaxone is preferred due to daily dosing versus 4-6x per day for penicillin; oral antibiotics are generally not recommended for treatment of IE

64
Q

What is the recommended empiric treatment for high-risk patients with febrile neutropenia?

A

broad-spectrum anti-pseudomonal agents (e.g. cefepime, meropenem, piperacillin-tazobactam)

note: fluoroquinolone monotherapy is not recommended due to poor activity against anaerobes

65
Q

What is the recommended empiric treatment for infective endocarditis in IV drug users with native heart valves?

A

Vancomycin

covers methicillin-resistant S. aureus, streptococci, and enterococci