Spot Dx — What on earth is this foot lesion?
Jason, a 30-year-old plumber, attends his GP regarding a lesion on his left foot. He says it started a week ago, shortly after he returned from Thailand.
The lesion began as an itchy red spot, and one week later has developed into the serpiginous lesion seen in the picture below.
Jason reports feeling otherwise well. He has no medical history of note, and the remainder of his physical examination is unremarkable.
He denies having any unprotected intercourse while away and reports no sexual health concerns or symptoms.
Temporary relief from the associated pruritus has been provided by using antihistamines.
Correct!
The answer is b. Cutaneous larva migrans (CLM) is a clinical syndrome consisting of an erythematous migrating linear or serpiginous cutaneous track.1
It commonly occurs because of human infection with the larvae of the cat or dog hookworms, Ancylostoma braziliense or Ancylostoma caninum. It can also be caused by the larvae of other animal parasites that are not natural human parasites.
CLM caused by an animal hookworm is commonly referred to as hookworm-related cutaneous larva migrans (HrCLM).1
CLM is mostly found in tropical and subtropical areas, including southwestern United States and northern Australia. It has become endemic in the Caribbean, Central America, South America, Southeast Asia and Africa.
Warm and humid conditions found in such tropical climates are conducive to the hatching of infective larvae.2,3
The infection of a human host often occurs due to lying, sitting or walking barefoot on ground contaminated with animal faeces. CLM remains confined to the outer layers of the skin as the larvae cannot penetrate the basement membrane to invade the deeper layers.3
Infected individuals may have intense localised pruritus, commencing soon after the hookworm penetrates the skin. Swollen erythematous or fluid-filled lumps, and snake-like tracts appear as the condition progresses. Multiple lesions may be found in a single person.3 The condition most frequently affects the lower extremities, abdomen or buttocks.
Blistering lesions, non-specific dermatitis and superimposed bacterial infection can make CLM a more challenging diagnosis. CLM is self-limiting. Resolution of symptoms varies considerably depending on the species of larvae involved.
In most cases, lesions will resolve without treatment within 4-8 weeks, but some may persist for many months.
Diagnosis is usually based on clinical findings, and skin biopsies can be used where doubt remains.
Prevention is imperative. Encourage patients to wear shoes when walking in sandy areas; to avoid lying on dry sand, even on a towel; and to avoid tropical beaches frequented by cats or dogs.3
Even though the condition is self-limiting, treatment can be used to shorten its course and to alleviate symptoms. Early and small localised lesions can be treated with topical thiabendazole.
Anthelmintics, such as mebendazole and ivermectin, can also be called upon with effective outcomes. Antihistamines and topical corticosteroids are useful for symptomatic relief, with antibiotics reserved for superimposed infections.3
What is the most likely diagnosis?
Jason, a 30-year-old plumber, attends his GP regarding a lesion on his left foot. He says it started a week ago, shortly after he returned from Thailand.
The lesion began as an itchy red spot, and one week later has developed into the serpiginous lesion seen in the picture below.
Jason reports feeling otherwise well. He has no medical history of note, and the remainder of his physical examination is unremarkable.
He denies having any unprotected intercourse while away and reports no sexual health concerns or symptoms.
Temporary relief from the associated pruritus has been provided by using antihistamines.