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Actinomycetoma — SCE Infectious Diseases MCQ

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ModerateTropical & Imported InfectionsActinomycetomaSCE Infectious Diseases

A 35-year-old man from rural India presents with a painless firm subcutaneous swelling on his jaw that has been slowly enlarging for 2 years. It drains yellowish-white grains through a sinus tract. Biopsy shows filamentous Gram-positive organisms that are NOT acid-fast. What is the most likely diagnosis?

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Correct answer: D — Actinomycetoma (bacterial mycetoma) — Gram-positive filamentous organisms that are NOT acid-fast suggest Actinomadura or Streptomyces

Yellowish-white grains with Gram-positive non-acid-fast filamentous organisms indicate actinomycetoma (bacterial). The key organisms are Actinomadura (non-acid-fast), Streptomyces (variably acid-fast), and Nocardia (partially acid-fast). Actinomycetoma is treated with prolonged antibiotics: Co-trimoxazole plus Amoxicillin (or Dapsone) for 3–12 months, with surgical debridement for large lesions. This differs from actinomycosis (Actinomyces israelii — forms sulphur granules, not mycetoma grains; treated with Penicillin) and eumycetoma (fungal — dark grains, requires antifungals).

Reference: WHO 2024 – Mycetoma; ISHAM 2020 – Mycetoma classification