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Another summertime condition...
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A healthy 14-year-old male presents with a rash on the sole of his left foot. He first noticed that there was something there 1 to 2 weeks earlier and that it was pruritic. There have been no other associated complaints, disturbing symptoms or fever. His past medical history is unremarkable, and his family history reveals no sick contacts or anyone else with skin or foot problems. His travel history, however, reveals that he spent 7 days at a tropical beach resort with his family. They had returned home about 1 week before the foot lesion was first noted.
Examination reveals normal vital signs and a healthy 14-year-old male, with the only positive finding being a linear, serpiginous erythematous lesion (Figure 1). There is a small papule that the patient noticed initially at the onset of itching (Figure 2).
What’s your diagnosis?
A. Scabies
B. Foreign body
C. Cercarial dermatitis
D. Hookworm disease
This is a classic case of cutaneous larva migrans (CLM), representing the invasion and migration within the skin of the hookworm larva (choice D). It is most commonly caused by the larvae of the dog or cat hookworm, Ancylostoma braziliense. The hookworm eggs are deposited in the soil (or beach sand) by the carrier host, from which the larvae hatch and seek another host. They can penetrate intact skin, but the human is not an appropriate host, so after several weeks, the larva dies and the life cycle ends. As such, usually no treatment is necessary, but many will use ivermectin or albendazole to speed up the process and prevent the remote chance of systemic spread. This patient was treated with albendazole and experienced a rapid recovery (Figure 3).
Most primary care providers are very familiar with scabies and the typical appearance of the skin lesions, including those areas damaged by intense scratching. However, babies have a tendency to have scabies on the palms and soles of the feet (Figure 4) as well, where they can appear as slightly raised macules or even larger lesions that have a pustular appearance. There is usually no confusing scabies with serpiginous lines of CLM.
A foreign body in the sole of the foot can take on many appearances, but obviously, there would be some history of trauma, usually to the forefoot as the shoeless patient swings the foot forward and catches a splinter or other foreign object in the process (Figure 5).
Cercarial dermatitis is often referred to as swimmer’s itch. This results from the swimmer or sunbather (lying on a beach) being infected by the cercariae, usually of an avian Schistosoma species, after emerging from the intermediate host, which is usually a snail or other mollusk. However, schistosomes seen in the United States are not adapted for humans and will soon die, ending the cycle. In the meantime, they can provoke an inflammatory reaction, resulting in pruritic, erythematous papules, some of which may have a pustular appearance. On subsequent exposures, a more severe reaction can occur (Figure 6).
While the patient presented may have spent a week on the beaches of a foreign tropical resort, the classic, serpiginous appearance of the lesion on the sole of his foot is virtually diagnostic and should not be confused with swimmer’s itch.
Columnist’s comments: Thanks to Brent Steadman, MD, a pediatrician in Abilene, Texas, and one of our former Scott & White residents, for contributing this interesting summertime case.
- For more information:
- James H. Brien, DO, is with the department of infectious diseases at McLane Children’s Hospital, Baylor Scott & White Health, and an adjunct professor of pediatrics at Texas A&M College of Medicine in Temple, Texas. He also is a member of the Infectious Diseases in Children Editorial Board. Brien can be reached at jhbrien@aol.com.
Disclosure: Brien reports no relevant financial disclosures.