Case Study - Diagnosing an itchy rash

Growth in foreign travel means this condition is presenting more, say Dr John Carey and Dr Sidhu Gada.

The larvae of cutaneous larva migrans roam haphazardly in the epidermis (Photograph: Author Image)
The larvae of cutaneous larva migrans roam haphazardly in the epidermis (Photograph: Author Image)

Recently, our surgery has seen two similar cases of a dermatological condition that is unusual in UK general practice.

An itchy rash
The first patient was initially seen out-of-hours for an itchy rash on her foot. She was treated with antihistamines, and had also tried OTC medicines, without success.

On further questioning, she revealed that she had recently visited Africa. A raised eosinophil count helped us to reach the diagnosis of cutaneous larva migrans.

The second case also presented as an itchy rash on the leg and because we were unsure of the diagnosis, we sought a second opinion from the London School of Hygiene and Tropical Medicine, which confirmed the diagnosis of cutaneous larva migrans.

It transpired that this patient had also recently travelled to an African country. They had both walked barefoot in sandy regions and had bathed in local pools without being aware that they were potentially exposing themselves to an infection of this type.

The patient presented with an itchy rash on her foot and was trea­ted with antihistamines without success (Photograph: Author Image)

A rare presentation
Cutaneous larva migrans is a rare presentation in UK clinical practice. However, the ease of foreign travel means cutaneous larva migrans is becoming a more common. Thus it should be included in the differential diagnosis of serpiginous pruritic lesions.

Cutaneous larva migrans is usually confined to the skin of the feet, buttocks or abdomen. It is caused by dog and cat hookworm (Ancylostoma braziliense) larvae, which are most commonly found in tropical and subtropical climates.

Hookworm eggs pass through the host animal and are deposited in its faeces. The eggs optimally hatch in the warm, shady, moist and sandy soil found in tropical and subtropical areas.

Humans are usually infected by walking barefoot on the sand. Larvae that come into contact with human skin can penetrate through hair follicles and tiny skin cracks. They then migrate underneath the skin. Unlike in their animal hosts, hookworm larvae cannot penetrate the dermis in humans, limiting their activity to the outer layers of the skin.

In animal hosts, penetration of the dermis and passage of the larvae into the venous and lymphatic system allows their transportation to the lungs, and migration to the trachea leads to swallowing of the larvae. In the intestine the larvae mature and produce eggs, which pass through the gut, completing the life cycle.

In humans, migration of larvae produces a 2–4mm wide, erythematous, elevated, vesicular serpiginous track. There may be associated vesiculobullous and papular lesions.

Migration through the skin occurs from a week to several months after initial penetration, depending on the species of hookworm. The rate of migration varies from 2mm to 2cm per day, depending on the species.

Because they cannot penetrate the epidermal basement membrane of human skin, the larvae roam haphazardly in the epidermis.

An allergic immune response of the patient to the larva or its by-products causes the pruritic erythematous track.

The actual location of the larva is usually around 2cm beyond the track. Untreated lesions resolve after the larva dies (which occurs within weeks to months).

The recommended treatment for this infection is either albendazole or thiabendazole, which are both OTC medicines but neither of these could be found locally.

Therefore, mebendazole 100mg twice daily was tried as an alternative and this successfully cleared the infection in both cases.

Who is at risk?
  • Sunbathers.
  • Anglers.
  • Hunters.
  • Gardeners.
  • Construction workers.
  • Pest exterminators.
  • Children.
  • Anyone with skin contact to sand or soil in tropical/subtropical areas.
  • Dr Carey and Dr Gada are GP principals at Holbrook and Shotley surgeries, Ipswich.

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