Cutaneous larva migrans — DTM&H MCQ

Correct answer: B — Cutaneous larva migrans

The correct answer is B, cutaneous larva migrans. This presentation, an intensely itchy, serpiginous track on the sole after walking barefoot on a tropical beach, is the classic history for hookworm-related cutaneous larva migrans, caused by animal hookworm larvae (usually Ancylostoma braziliense) penetrating the skin from sand contaminated with dog or cat faeces. The lesion is afebrile and advances slowly over days rather than hours, which fits the described clinical course. The feet are the most commonly affected site because larvae penetrate at the point of skin contact with contaminated sand, and the track corresponds to the larva's slow migration through the epidermis. Why the other options are wrong: A. Mycetoma: this is a chronic, painless, indurated swelling with sinus tracts and grain discharge from fungal or bacterial infection following penetrating injury, not a rapidly itchy migrating linear track. D. Scabies: produces burrows typically in web spaces, wrists and genitals from mite tunnelling, causing generalised nocturnal itch rather than a single elongating serpiginous track on the sole. E. Tungiasis: caused by the burrowing female sand flea (Tunga penetrans), producing a painful papule with a central black punctum, usually on the foot, but it does not create a migrating serpiginous track. C. Larva currens from Strongyloides: also serpiginous and pruritic, but migrates extremely rapidly (several centimetres per hour) and typically affects the perianal area, buttocks or thighs from autoinfection, unlike the slow, day-by-day advance on the sole described here. Key point: a slowly advancing (centimetres per day), pruritic, serpiginous track on the foot after barefoot beach exposure is cutaneous larva migrans; a rapidly moving (centimetres per hour) perianal or truncal track points instead to Strongyloides larva currens.

Reference: Patient.info (Doctor) / GP clinical reference, Cutaneous Larva Migrans, reviewed 2023, https://patient.info/doctor/cutaneous-larva-migrans