Microsporidiosis — SCE Infectious Diseases MCQ

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HardHIV MedicineMicrosporidiosisSCE Infectious Diseases

A 45-year-old man with advanced HIV (CD4 22 cells/µL) presents with chronic watery diarrhoea and weight loss. Modified trichrome stain of stool shows small (1–2 µm) oval spores with a characteristic equatorial band. What is the most likely diagnosis?

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Correct answer: A — Microsporidiosis (Enterocytozoon bieneusi)

Small (1–2 µm) oval spores with an equatorial band on modified trichrome stain are diagnostic of Microsporidia. Enterocytozoon bieneusi is the most common species causing diarrhoea in advanced HIV. Treatment is primarily immune reconstitution with ART. Albendazole 400 mg BD has activity against Encephalitozoon species but is less effective against E. bieneusi. Fumagillin has activity against E. bieneusi but is limited by toxicity. Cryptosporidium oocysts are 4–6 µm and appear on modified ZN stain.

Reference: BHIVA 2022 – OI guidelines; WHO 2021 – Microsporidiosis in HIV