Two students, 2 tropical beaches, 2 injured feet
Diagnosis: Cutaneous larva migrans
Cutaneous larva migrans (CLM, sometimes called the “creeping eruption”) occurs when the third-stage larvae of dog (or cat) hookworm (Ancylostoma braziliense and A caninum, most commonly) invade the skin and fail to penetrate the epidermal basement layer. Humans are not the definitive host for this roundworm. Skin manifestations occur due to a hypersensitivity reaction.
The disease is found most commonly in tropical and subtropical climates. Animals defecate on warm, moist sand and the nematode eggs hatch. The larvae quickly invade bare skin in contact with the sand. The highest incidence of infection in the US occurs in Florida and along the Gulf Coast, but the disease is more common in the Caribbean, Central and South America, and Southeast Asia and Africa.
Many patients report a stinging sensation when the larva penetrates, as did patients 1 and 2, who misinterpreted the pain as a puncture (patient 1) or an insect bite (patient 2). Larvae migrate at a rate of several millimeters per day. Migration produces an intensely pruritic, linear or serpiginous track 2 to 4 mm wide, sometimes with vesicles, as the body reacts to the larva or to its excreta. Because each larva leaves an individual track in its wake, lesions may be simple or quite complex, depending upon the number of infecting organisms. A second morphologic variant has been described with follicular papules and pustules accompanying linear burrows.1 Eventually, the larvae die and the condition resolves even without treatment, but treatment accelerates resolution. The lesions may occur anywhere on the body, but most commonly are found on the feet, buttocks, and hands.
Differential diagnosis
The typical lesion is usually a straightforward diagnosis (once the observer is familiar with the infection), but differential diagnosis includes tinea corporis, granuloma annulare, erythema migrans (Lyme disease), ground itch, larva currens, myiasis, and stings by marine invertebrates. In very rare cases, larvae may migrate to the lungs, causing pneumonitis.2
