Congratulations to the readers who wrote in with the correct answer! You all realized that the large size of a foreign appearing organism embedded in skin, combined with the suggestive history, is consistent with Tungiasis. Another commenter gets special bonus points for the entertaining answer “gel foam with eggs”. I think that most pathologists would think the same thing when faced with this interesting and complex appearing arthropod on H&E.
Thankfully, the diagnosis can easily be made with a rudimentary knowledge of this organism, (that is, without entomology training). The presence of the complex internal structures indicates that this is an arthropod and not a foreign body such as a splinter. The large size rules out the diagnosis of scabies. Helpful features include the thick brown exoskeleton and eggs in cross-section (see image). Other diagnoses to consider include cutaneous myiasis (infection with fly larvae), tick mouth parts, and cutaneous larva migrans.
(CLICK ON IMAGE TO ENLARGE)
Tungiasis, also known as ‘jiggers’, is a condition caused by infestation with the fertilized female flea Tunga penetrans (a.k.a. ‘jigger flea’ or ‘chigoe’). This is the only flea to burrow into human skin; she buries in head first and feeds on blood from the dermal capillaries. Her posterior end remains exposed so that she may release her eggs. Eventually, she may reach the size of a pea. The presence of the foreign object in the epidermis and dermis results in abscess formation, and frequently, secondary bacterial infection.
Tungiasis is prevalent in Sub-Sarahan Africa, Central and South America, and the Carribean - including some popular vacation destinations! Exposure to the sand flea occurs while walking barefoot on the beach, so protective footwear is required for prevention. Infestation typically occurs on the feet around the nails, but other sites include the thighs, buttocks, abdomen and hands. Treatment is sterile removal of the lesion.
Thanks for reading. Answers and new cases are posted every Monday!