Changing paradigms in parasitic infections: common dermatological helminthic infections and cutaneous myiasis.

Parasitic diseases caused by helminths, or worms, account for billions of human infections worldwide. Although most human pathogens caused by these organisms are infrequent in the United States, skin manifestations of parasitic diseases are being seen much more frequently in dermatologists' offices due to the increase in immigration and travel. Helminths are notable for their complicated lifecycles often including consecutive developmental phases, in separate hosts or in a free-living state. These parasitic organisms are usually macroscopic, multicellular organisms, and do not breed within their mammalian hosts. Notably, many helminthic diseases present with dermatologic signs and symptoms including skin nodules, cysts, migratory skin lesions, and pruritus. In this section, we discuss cutaneous myiasis as well as the four most common nematode dermatologic conditions seen in the United States.