A traveller returning from coastal East Africa reports an intensely itchy, tender nodule beneath the margin of her toenail, with a central dark spot and a surrounding halo of erythema. The lesion developed over about a week after walking barefoot on a sandy beach. The causative agent is:

• A Sarcoptes scabiei var hominis
• B Dermatobia hominis
• C Ancylostoma duodenale
• D Tunga penetrans ✓

Explanation

Tungiasis is caused by the gravid female sand flea Tunga penetrans, which burrows into plantar skin, periungual areas and toes, leaving a central dark dot representing the flea's posterior abdomen through which eggs are shed. Scabies burrows are thread-like and interdigital, hookworm larvae migrate as serpiginous tracks, and Dermatobia produces furuncular boils elsewhere on the body.

Reference: Rook's Textbook of Dermatology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.