Infectious Disease

Question 1

Give the opportunistic infections in HIV, their associated CD4 count, and prophylaxis

Answer 1

1. Pneumocystis jiroveci: CD4 <200, TMP-SMX (Alt. Dapsone, Atovaquone, Pentamidine)
2. Toxoplasma gondii: CD4 <100 and positive IgG. TMP-SMX (Alt. Dapsone + Pyrimethamine + Leucovorin)
3. Histoplasma capsulatum: CD4 <150 and endemic area. Itraconazole
4. Varicella Zoster: Close contact with chicken pox/shingles AND no prior hx of dz or negative Ab. VariZIG or IVIG within 4 days of exposure

Question 2

Differentiate radiographic findings of Primary CNS Lymphoma (PCL) from Toxoplasma encephalitis

Answer 2

Both are ring-enhancing lesions with edema and mass effect

Features that suggest PCL: solitary lesions, lesions >4cm, involvement of corpus callosum, periventricular, or periependymal areas

Toxo commonly involves the basal ganglia

Question 3

Give criteria for a complicated parapneumonic effusion and treatment

Answer 3

pH <7.2
Glucose <60
WBC >50,000
LDH >1000

Positive Gram stain

Needs chest tube

Question 4

Give the induration cutoffs for TB skin test

Answer 4

> 5mm: HIC, contacts of pt with known TB, organ transplant recipients and other immunosuppressed persons

> 10mm: Recent immigrants (<5 years) from endemic areas, IV drug users, high risk setting residents/employees, higher risk conditions (diabetes, leukemia, ESRD)

> 15mm: Everyone else