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Disseminated Histoplasmosis — RACP Adult Medicine MCQ

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HardInfectious DiseasesDisseminated HistoplasmosisRACP Adult Medicine

A 40-year-old man presents with a 2-month history of fevers, weight loss, and tender subcutaneous nodules on his legs. He has lived in Far North Queensland. Biopsy of a nodule shows granulomas with central necrosis and 'ghost outlines' of fungi with broad-based budding. What is the most likely organism?

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Correct answer: B — Histoplasma capsulatum

While Histoplasma capsulatum and Blastomyces dermatitidis are the classic broad-based budding dimorphic fungi, Histoplasma is endemic in certain parts of Australia (particularly caves in Queensland – bat exposure) and presents with disseminated disease (fever, weight loss, hepatosplenomegaly, skin nodules, pancytopaenia). The diagnosis is confirmed by fungal culture, histopathology, or urinary Histoplasma antigen. Disseminated histoplasmosis is treated with liposomal amphotericin B for induction followed by oral itraconazole for 12 months. HIV testing should be performed.

Reference: eTG – 2025 – Antibiotic Guidelines; CDNA – 2024 – Histoplasmosis