Tropical ulcer — DTM&H MCQ

Correct answer: E — Tropical ulcer

The correct answer is E, Tropical ulcer. This adolescent has the classic picture: malnutrition, minor trauma triggering a rapidly enlarging, painful lower-leg ulcer with foul-smelling discharge and mixed (polymicrobial) bacterial growth on culture. Tropical (phagedenic) ulcer arises from synergistic infection with anaerobic and aerobic organisms in the setting of poor nutrition, skin trauma, and humid tropical conditions exactly as described here. The rapid tissue necrosis, pain, and offensive discharge reflect the destructive, mixed-flora nature of the infection rather than a single specific pathogen, distinguishing it from the other listed conditions. Why the other options are wrong: A. Cutaneous leishmaniasis: produces a painless, slowly evolving nodulo-ulcerative lesion with a clean, often volcano-shaped edge, not a rapidly progressive, foul-smelling, painful ulcer with mixed bacterial growth. D. Tungiasis: caused by the burrowing sand flea Tunga penetrans, presenting as a painful papule with a black dot on the foot, not a large enlarging ulcer with purulent discharge. B. Eumycetoma: a chronic, painless, indolent swelling of the foot or leg with sinus tracts discharging grains over months to years, not an acutely painful rapidly enlarging ulcer. C. Buruli ulcer: Mycobacterium ulcerans infection classically begins as a painless nodule or plaque that progresses with little or no pain due to the local immunosuppressive mycolactone toxin, contrasting sharply with the pain described in this vignette. Key point: A painful, rapidly enlarging, foul-discharging ulcer with mixed bacterial growth in a malnourished patient after minor trauma points to tropical ulcer, whereas painless, indolent progression should suggest Buruli ulcer.

Reference: WHO Fact Sheet: Buruli ulcer (Mycobacterium ulcerans infection), 2023, https://www.who.int/news-room/fact-sheets/detail/buruli-ulcer-(mycobacterium-ulcerans-infection) (used to confirm the painless clinical course of Buruli ulcer as the key discriminator from tropical ulcer)