Talaromycosis in HIV — DTM&H MCQ

Correct answer: E — Talaromycosis

The correct answer is E, Talaromycosis. This patient has advanced HIV (a low CD4 count implied by disseminated disease) and presents with the classic triad of fever, hepatosplenomegaly and umbilicated papules acquired in northern Thailand, the endemic heartland for Talaromyces marneffei. The clinching microbiological clue is the dimorphic fungus producing a diffusible red pigment on culture, a signature feature of T. marneffei that distinguishes it from other endemic dimorphic fungi. This organism grows as a mould at 25 to 30C producing the red pigment and converts to a yeast form at 37C, and disseminated infection in advanced HIV closely mimics disseminated histoplasmosis or cryptococcosis clinically, so geography plus the pigment are the discriminators the question is testing. Why the other options are wrong: A. Disseminated cryptococcosis: Cryptococcus neoformans is an encapsulated yeast, not a dimorphic mould, and does not produce red pigment; India ink or cryptococcal antigen would confirm, not culture pigment. B. Mpox: causes vesiculopustular skin lesions with lymphadenopathy but is a viral infection, so blood culture would never yield a fungus. C. Molluscum contagiosum alone: molluscum causes umbilicated papules in advanced HIV but is a poxvirus infection of skin only, with no systemic fever, hepatosplenomegaly or positive blood culture. D. Histoplasmosis: Histoplasma capsulatum is also dimorphic and can cause an identical clinical picture in advanced HIV, but it does not produce a red diffusible pigment and is more typically linked to the Americas or bat/bird guano exposure rather than northern Thailand. Key point: In an HIV patient from Southeast Asia with umbilicated papules, a dimorphic fungus that produces red pigment on culture is diagnostic of Talaromyces marneffei (talaromycosis), not histoplasmosis.

Reference: BHIVA/British Infection Association Guidelines on the Management of Opportunistic Infection in People Living with HIV (talaromycosis, formerly penicilliosis, listed among fungal OIs endemic to Southeast Asia); HIV Medicine 2020/2011, https://www.bhiva.org/OI-guidelines