Infectious Disease II Flashcards
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.
Ehrlichiosis
carried by ticks, including the lone star tick (Amblyomma americanum), in southeastern and south central United States
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.
Legionella pneumoniae (Legionnaire’s disease)
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.
Chancroid (Haemophilus ducreyi infection)
uncommon in the U.S. but outbreaks have occured in those who trade sex for drugs/money
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?
Herpes zoster (shingles)
What is the likely diagnosis in a patient that recently returned from a trip to Kenya and presents with headache, fatigue, and episodic fever?
Malaria
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.
Trichinellosis
usually due to ingestion of undercooked pork in endemic areas
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?
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)
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?
Vertebral osteomyelitis
most likely due to hematogenous spread of the UTI; initial workup includes CBC, blood cultures, ESR/CRP, and plain spinal X-rays
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.
Cervicofacial Actinomyces infection
gram stain often shows filamentous, branching gram-positive rods
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.
Progressive multifocal leukoencephalopathy (PML)
reactivation of JC virus primarily occurs in patients with CD4+ count < 200/mm3
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.
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)
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?
Mucormycosis
What is the likely diagnosis in a patient with poorly controlled HIV that develops multiple violaceous papules in the groin region?
Kaposi sarcoma (HHV-8 infection)
may require biopsy (lymphocytic infiltrate) to help differentiate from bacillary angiomatosis (neutrophilic infiltrate)
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.
Viral esophagitis
e.g. due to HSV (circular ulcers) or CMV (linear ulcers); Candida esophagitis is associated with oral thrush and mild odynophagia
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
Toxoplasma encephalitis
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.
Cryptococcal meningoencephalitis
diagnosis is established by CSF testing for cryptococcal antigen, India ink stain, or culture on Sabouraud agar
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.
Neurocysticercosis
caused by ingestion of food/water contaminated with Taenia solium (pork tapeworm) eggs
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)?
Acute hepatitis A infection
most patients completely recover in 3 - 6 weeks
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.
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
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.
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
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?
autoimmune hemolytic anemia
due to IgM (cold-agglutinin) antibodies that cross-react with EBV and RBCs/platelets
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?
Jarisch-Herxheimer reaction
due to rapid lysis of spirochetes; self-limited and resolves spontaneously within 48 hours
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?
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)
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.
Mycoplasma pneumoniae infection (atypical pneumonia)
patients may also have mild hemolytic anemia due to cold agglutins; treatment is empiric macrolide or respiratory fluoroquinolone therapy
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.
Infectious mononucleosis
heterophile antibodies may be falsely negative early in the illness; atypical lymphocytes are suggestive of infectious mononucleosis
What is the likely diagnosis in a young adult with grey mucosal patches in the mouth, epitrochlear lymphadenopathy, and a diffuse maculopapular rash?
Secondary syphilis
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%
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)
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
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
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?
Echinococcus granulosus infection
lack of fever and cystic lesion favor echinococcus rather than entamoeba histolytica (febrile with a smooth, cystic subcapsular mass)
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.
Coccidioides immitis infection
causes community-acquired pneumonia symptoms, often with arthralgias and erythema nodosum; endemic to Southwestern U.S.
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)?
Mycobacterium tuberculosis infection
reactivation TB preferentially infects the lung apices and presents with subacute or chronic symptoms; reactivation is more common in HIV patients
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?
Cryptococcal meningoencephalitis
caused by Cryptococcus neoformans, typically in HIV patients with CD4+ count < 100
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.
Pneumocystis pneumonia
severe hypoxia and bilateral interstitial infiltrates in an HIV patient with CD4+ < 200/mm3 favors this diagnosis
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.
Disseminated Mycobacterium avium complex (MAC) infection
TB and CMV are less likely given the normal CXR, induration, and negative CMV IgG
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)?
Miliary tuberculosis
most common behavioral risk factor for TB in the United States is substance abuse
What is the likely microorganism causing a UTI in a young female with an elevated urine pH and renal calculus on imaging?
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)
What is the likely result of the following serologic tests in a patient naturally immunized against hepatitis B?
HBsAg: […]
HBsAb: […]
HBcAb: […]
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
What is the likely result of the following serologic tests in a patient vaccinated against hepatitis B?
HBsAg: […]
HBsAb: […]
HBcAb: […]
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
What is the likely result of the following serologic tests in a patient with chronic hepatitis B?
HBsAg: […]
HBsAb: […]
HBcAb: […]
What is the likely result of the following serologic tests in a patient with chronic hepatitis B?
HBsAg: positive
HBsAb: negative
HBcAb: positive
What is the likely underlying infection in a patient with recurrent blisters on sun-exposed areas with fatigue, nausea, and elevated LFTs?
Chronic hepatitis C infection
What is the most common cause of community-acquired pneumonia in HIV patients?
Streptococcus pneumoniae
presents similarly to bacterial CAP in HIV-negative individuals
What is the most common manifestation of carditis secondary to Lyme disease?
AV block
What is the most common microorganism causing infective endocarditis in IV drug users?
Staphylococcus aureus
typically involves the tricuspid valve (right-sided)
What is the most common source of infection causing Ludwig angina?
Infected mandibular molar (dental infection)
What is the most common symptom of bacterial endocarditis?
Fever
mnemonic: FROM JANE
What is the most reliable sign for vertebral osteomyelitis?
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)
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?
Fluorescent treponemal antibody absorption (FTA-ABS)
FTA-ABS has higher sensitivity in patients with primary syphilis compared to non-treponemal tests (see below)
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?
draw blood for HIV serology and start anti-retroviral therapy with 3 drugs immediately
preferred regimen is tenofovir-emtricitabine with raltegravir for 4 weeks
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?
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)
What is the next step in management for a patient found to have positive HCV antibodies?
Hepatitis C RNA testing
diagnosis must be confirmed as up to half of patients may spontaneously clear the virus
What is the next step in management for a patient that develops fever, malaise, splinter hemorrhages, and aortic regurgitation following a dental procedure?
Obtain blood cultures
blood cultures should be obtained before initiating antibiotic therapy or obtaining cardiac imaging in patients with suspected infective endocarditis
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.
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
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?
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
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.
Oral fluconazole
if symptoms do not resolve with oral fluconazole, endoscopy is warranted
What is the next step in management for a patient with poorly controlled HIV that presents with mild odynophagia/dysphagia?
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)
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.
Switch to oral TMP-SMX
most hospitalized patients can be transitioned to culture-guided oral antibiotics if symptoms are improved at 48 hours
What is the next step in management for a patient with suspected ventilator-associated pneumonia with a CXR demonstrating lobar infiltrate?
Gram stain/culture of respiratory secretions
should be obtained prior to administering empiric antibiotics
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?
MRI
followed by CT-guided bone biopsy if positive
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.
No additional intervention required
in the US, an induration size of
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?
Isoniazid and pyridoxine
this patient should be treated for latent TB
What is the preferred diagnostic test for Babesiosis?
Peripheral blood smear (“Maltese cross”)
treatment typically is atovaquone + azithromycin (quinine + clindamycin may be used for severe infections)
What is the preferred treatment for a patient with cervicofacial actinomyces infection?
Pencillin
What is the preferred treatment for a patient with infective endocarditis secondary to penicillin-sensitive Streptococcus mutans?
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
What is the recommended empiric treatment for high-risk patients with febrile neutropenia?
broad-spectrum anti-pseudomonal agents (e.g. cefepime, meropenem, piperacillin-tazobactam)
note: fluoroquinolone monotherapy is not recommended due to poor activity against anaerobes
What is the recommended empiric treatment for infective endocarditis in IV drug users with native heart valves?
Vancomycin
covers methicillin-resistant S. aureus, streptococci, and enterococci
