HIV exposure and infection in children — formative SAQs

SAQ 1 (10 marks)

A term infant is born to a 26-year-old mother whose HIV is well controlled on combination antiretroviral therapy, with an undetectable viral load at delivery. The mother intends to formula-feed. Outline the management of this HIV-exposed infant from birth until infection is confidently excluded. [7]

Question: Describe the stepwise management of this HIV-exposed infant, including infant prophylaxis, cotrimoxazole, diagnostic testing and follow-up. (10 marks) [7]

Model answer

Infant antiretroviral prophylaxis (2 marks). Because the mother is suppressed and the infant is low-risk, give nevirapine prophylaxis, typically for four to six weeks. State that a higher-risk infant — for example one born to a viraemic or newly diagnosed mother — would also receive zidovudine, and that the prophylaxis duration and regimen are matched to the transmission risk. [7]

Cotrimoxazole prophylaxis (2 marks). Start cotrimoxazole at four to six weeks of age and continue it until infection has been excluded, because Pneumocystis pneumonia is a leading cause of infant HIV mortality and prophylaxis is effective and cheap. State the principle: prophylaxis covers the window between exposure and a confident exclusion of infection. [8]

Diagnostic testing — PCR, not antibody (3 marks). The diagnosis of infant HIV uses HIV DNA or RNA PCR, because maternal IgG crosses the placenta and persists for up to 18 months, making antibody testing uninterpretable in the infant. Perform a PCR at four to six weeks; because this infant is low-risk and replacement-fed, a birth PCR is not strictly required but is often included. A negative result early does not exclude late infection, so confirm with a final HIV antibody test at 18 to 24 months, when maternal antibody has cleared. A single positive PCR must be confirmed with a second sample before labelling the child infected. [7]

Feeding, follow-up and the family layer (3 marks). Because the mother is formula-feeding, support safe replacement feeding and confirm access to clean water and reliable supply. Ensure the mother remains on lifelong ART (Option B+) with continued viral suppression, offer partner and sibling testing, and reinforce that the suppressed maternal viral load is the single strongest predictor of no transmission. Arrange structured follow-up through the specialist paediatric HIV service until the final antibody test is negative and the chapter is closed. [3] [7]

SAQ 2 (10 marks)

A 4-month-old infant born to a mother known to be HIV-positive but disengaged from care presents to the emergency department with a three-day history of worsening cough, marked tachypnoea and oxygen saturation of 86% in air. The chest X-ray shows diffuse bilateral interstitial infiltrates. The infant has never had an HIV PCR and is not on any prophylaxis. [8]

Question: (a) What is the most likely diagnosis, and what is your immediate management? (b) Outline the diagnostic approach and the definitive management once the infant is stabilised. (c) Explain why antibody testing alone would be inadequate in this infant. (10 marks) [8]

Model answer

(a) Likely diagnosis and immediate management (4 marks). The most likely diagnosis is Pneumocystis jirovecii pneumonia in an HIV-exposed, unprophylaxed infant of an unsuppressed mother — the classic age (three to six months), the hypoxia out of proportion to auscultatory findings, and the diffuse interstitial infiltrates. Immediate management is oxygen, admission for monitoring, and empiric high-dose co-trimoxazole with a corticosteroid for moderate–severe disease while the diagnosis is pursued. Do not delay treatment to confirm — PCP progresses rapidly and delay kills. [8]

(b) Diagnostic approach and definitive management (4 marks). Send an HIV DNA or RNA PCR to confirm infant infection, and pursue the PCP diagnosis with a chest X-ray (already done) and, where available, induced sputum or nasopharyngeal wash for Pneumocystis. Once the infant is stable, start antiretroviral therapy immediately if infection is confirmed — the CHER trial showed that early ART in infants reduced mortality by about 76%, and treat-all guidance applies to every infected child regardless of age or stage. Continue cotrimoxazole prophylaxis and provide nutrition, growth and opportunistic-infection care. [1] [5]

(c) Why antibody is inadequate (2 marks). Maternal IgG crosses the placenta and persists in the infant's blood for up to 18 months, so a positive HIV antibody test in this four-month-old reflects the mother, not the infant. Only nucleic-acid testing — HIV DNA or RNA PCR — can confirm or exclude infection at this age, and a single positive must be confirmed with a second sample. Antibody testing becomes reliable only after maternal antibody has cleared, at around 18 months. [7]