HIV exposure and infection in children — branching viva

Opening question

Examiner: Take me through this infant. What is the most likely diagnosis, and what is your immediate frame? ^[8]

Candidate: The most likely diagnosis is Pneumocystis jirovecii pneumonia in an HIV-exposed, unprophylaxed infant of an unsuppressed mother. The age — four months — the hypoxia out of proportion to auscultatory findings, and the diffuse bilateral interstitial infiltrates are the classic picture. My frame is two-layered: keep this infant alive now, and then confirm the HIV status and treat the underlying immunodeficiency. I would give oxygen, admit, start empiric high-dose co-trimoxazole with a corticosteroid for moderate–severe disease, and pursue the diagnosis. ^{[8] [1]}

Examiner: Why Pneumocystis specifically? ^[8]

Candidate: Because PCP is the opportunistic pneumonia of infant HIV, classically presenting between three and six months in an infected, unprophylaxed infant. The hypoxia is disproportionate to the chest findings, the X-ray shows diffuse interstitial infiltrates, and the infant of an unsuppressed, disengaged mother is exactly the child who acquires infection and is missed. The onset is subacute over days but can decompensate over hours, so I treat empirically while confirming. ^[8]