Acute Chagas disease — DTM&H MCQ

Correct answer: A — Chagas disease (acute phase)

The correct answer is A, Chagas disease (acute phase). Romana's sign, unilateral painless periorbital oedema caused by the triatomine bug depositing infected faeces near the eye during a bite, is the classic conjunctival portal-of-entry sign for acute Trypanosoma cruzi infection. The rural adobe housing history is a key epidemiological clue, since triatomine (reduviid) "kissing bugs" colonise cracks in mud brick walls and roofs in endemic Latin American regions. Fever plus circulating C-shaped trypomastigotes on blood film confirms parasitaemia, which is characteristic of the acute phase before the infection becomes latent (indeterminate) or progresses to chronic cardiac or gastrointestinal disease. Why the other options are wrong: E. African trypanosomiasis: caused by Trypanosoma brucei transmitted by tsetse flies in sub-Saharan Africa, not Brazil, and presents with a chancre and lymphadenopathy rather than Romana's sign. C. Orbital cellulitis: is a painful, tender, erythematous swelling with visual disturbance and systemic sepsis signs, whereas Romana's sign is classically painless, and no trypomastigotes would appear on blood film. B. Cutaneous leishmaniasis: produces chronic painless ulcerating skin lesions, not eyelid oedema, and diagnosis relies on amastigotes in tissue smears, not blood trypomastigotes. D. Toxoplasmosis with periorbital involvement: causes chorioretinitis or lymphadenopathy, not palpebral oedema, and is diagnosed serologically or via tissue cysts, not blood-film trypomastigotes. Key point: Romana's sign plus adobe-house exposure and C-shaped trypomastigotes on blood film in a Latin American patient is pathognomonic for acute Chagas disease.

Reference: GOV.UK, Chagas disease: migrant health guide (UK Health Security Agency), https://www.gov.uk/guidance/chagas-disease-migrant-health-guide