Master the board step 3

Master the Boards: USMLE Step 3
Prophylaxis
Pneumocystis jiroveci Pneumonia (PCP) (< 200 CD4 cells)
··
TMP/SMX is the best prophylaxis for PCP by far.
··
If TMP/SMX causes a rash, switch to atovaquone or dapsone. (Dapsone
cannot be used if there is G6PD deficiency.)
··
Aerosolized pentamidine has the poorest efficacy and is rarely used. There is
the most amount of breakthrough.
Mycobacterium Avium-Intracellulare (MAI) (< 50 CD4 cells)
··
Use azithromycin once a week orally.
Opportunistic Infections
PCP
This presents with shortness of breath, dry cough, hypoxia, and increased
LDH.
Diagnostic Testing
··
Best initial test: A chest x-ray will show increased interstitial markings
bilaterally.
··
Most accurate test: Bronchoalveolar lavage
Treatment
··
IV TMP/SMX
··
If there is a rash, use IV pentamidine or the combination of clindamycin
and primaquine.
··
Atovaquone can be used for mild pneumocystis.
··
Dapsone is not intravenous and is used for prophylaxis, not treatment.
··
If PCP is severe (pO 2 < 70 or A-a gradient > 35), then give steroids.
Ganciclovir: low WBC
Foscarnet: high creatinine
Toxoplasmosis
Look for headache, nausea, vomiting, and focal neurologic findings. Best initial
test is a head CT with contrast showing “ring” or contrast-enhancing lesions.
Treat with pyrimethamine and sulfadiazine for 2 weeks and repeat the CT
scan. If the lesions are smaller, then this is confirmative of toxoplasmosis. If the
lesions are unchanged in size, then perform a brain biopsy, since this is most
likely lymphoma.
Cytomegalovirus (CMV)
HIV with < 50 CD4 cells and blurry vision. Perform a dilated ophthalmologic
examination. CMV is diagnosed by the appearance of the lesions on examination.
Treat with ganciclovir or foscarnet.
32