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HIV opportunistic infection prophylaxis — ABIM Board MCQ

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ModerateInfectious DiseaseHIV opportunistic infection prophylaxisABIM Board

A 39-year-old man is newly diagnosed with HIV infection. His CD4 count is 82 cells/microL, HIV RNA level is 180,000 copies/mL, and Toxoplasma gondii IgG is positive. He has no symptoms suggesting an active opportunistic infection and no sulfonamide allergy. Antiretroviral therapy will be initiated promptly. Which of the following additional interventions is most appropriate?

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Correct answer: E — Start trimethoprim-sulfamethoxazole prophylaxis

The correct answer is trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis. Toxoplasma IgG positivity indicates prior infection, and a CD4 count below 100 cells/microL creates sufficient risk of reactivation and toxoplasmic encephalitis to warrant primary prophylaxis. TMP-SMX is preferred and also protects against Pneumocystis jirovecii pneumonia, for which this patient also qualifies while initiating ART with a CD4 count below 200 cells/microL. Azithromycin is used for Mycobacterium avium complex prophylaxis in selected patients with CD4 counts below 50 cells/microL who are not promptly starting suppressive ART. Routine fluconazole prophylaxis is not recommended. Isoniazid requires evaluation for latent tuberculosis or a qualifying exposure. ART should be initiated, but it does not eliminate the immediate need for indicated prophylaxis.

Reference: National Library of Medicine, Primary Care for Adults With HIV, Table 4: Opportunistic Infection Prophylaxis for Adults With HIV, March 2025. https://www.ncbi.nlm.nih.gov/books/NBK567851/table/table-4/?report=objectonly