Cutaneous leishmaniasis diagnosis — DTM&H MCQ

Correct answer: C — Skin sampling for microscopy, culture or PCR for Leishmania

The correct answer is C, skin sampling for microscopy, culture or PCR for Leishmania. A chronic, painless ulcer with a raised indurated edge in a returned traveller from a New World endemic area such as Belize, unresponsive to antibiotics and without systemic upset, is the classic presentation of cutaneous leishmaniasis transmitted by sandfly bite. UK public health guidance specifically flags leishmaniasis as a cause of non-healing ulcers that fail standard antimicrobial therapy and warrant specialist referral and targeted testing. Parasitological confirmation from the lesion itself (slit skin smear, biopsy or aspirate for microscopy, culture and PCR) remains the diagnostic approach, since molecular testing improves sensitivity over microscopy or culture alone and allows species identification, which matters because New World species carry a risk of mucosal spread and this influences treatment choice. Why the other options are wrong: A. Serum cryptococcal antigen: tests for a fungal pathogen causing meningitis or pulmonary disease in immunocompromised hosts, not a cause of indolent skin ulcers in an immunocompetent traveller. E. Blood film for microfilariae at midnight: used for lymphatic filariasis, which causes lymphoedema and hydrocele, not a solitary indurated ulcer, and Belize is not a filariasis exposure risk here. D. Urine microscopy for terminal-spined eggs: detects Schistosoma haematobium, causing haematuria and bladder disease, irrelevant to a forearm skin lesion. B. Widal test for enteric fever: an outdated, unreliable serological test for typhoid, a febrile systemic illness, not a chronic afebrile ulcer. Key point: A painless, indurated, antibiotic-unresponsive ulcer in a traveller from a leishmaniasis-endemic region should prompt lesion sampling (microscopy, culture, PCR) for Leishmania rather than serology or blood tests aimed at unrelated tropical infections.

Reference: UK Health Security Agency and Barts Health NHS Trust. Skin lesions in newly arrived migrants: recognising and managing infections of public health importance. GOV.UK, 2025. https://www.gov.uk/government/publications/skin-lesions-in-newly-arrived-migrants/skin-lesions-in-newly-arrived-migrants-recognising-and-managing-infections-of-public-health-importance