Foot infections and infestations

A pictorial guide to foot infections and infestations. Including Athlete's foot, Localised bacterial infection, Cellulitis or erysipelas, Plantar warts, Viral warts, Hand foot and mouth disease, Scabies and Cutaneous larva migrans.

 

Athlete's foot (tinea pedis)
Athlete's foot is common, especially in young men and the immunosuppressed. It presents with itching and peeling between and under the surface of the toes. The interdigital type is usually associated with Trichophyton mentagrophytes (interdigitale) or Epidermophyton floccosum. If necessary, the diagnosis may be confirmed by microscopy and culture of skin scrapings.

Topical imidazole or terbinafine cream is usually effective. To protect against recurrence, the patient should be advised about foot hygiene. Concurrent tinea cruris or tinea unguum would also require treatment. Localised bacterial infection

 

Localised bacterial infection
Cracked areas or open wounds, such as may occur in athlete's foot, are an open invitation for bacteria to infect the area, which becomes inflamed, hot and painful. Staphylococcus aureus or Staph epidermidis, or a streptococcus are the most usual causes. This can be confirmed and the sensitivities assessed by culture of a swab of the area.

For streptococcal infections, treatments include oral antibiotics such as penicillin V or amoxicillin (or clindamycin for allergic patients).

 

Cellulitis or erysipelas
Cellulitis and erysipelas are acute infections of the dermis and subcutaneous tissues, commonly affecting the lower limbs and feet. A well-defined, hot, rapidly spreading inflammation develops with tenderness and pain. Onset is sudden and may be associated with fever, rigours, nausea and vomiting, and enlarged regional lymph glands. Blood culture should be taken if septicaemia is suspected.

Analgesics and systemic antibiotics, including benzylpenicillin with flucloxacillin, or erythromycin if the patient is allergic to penicillin, are required. Treatment should continue for at least 7-10 days. In serious cases, hospital admission my be necessary.

 

Plantar warts
Plantar warts, or verrucas, are caused by infection with HPV and are acquired through direct contact with warts or autoinnoculation. Black dots visible in the middle of the scaly area are thrombosed capillary blood vessels. Untreated, 90 per cent of warts will disappear within two years.

For patients who request treatment, approaches include occlusion under duct tape, wart paints containing salicylic acid and cryotherapy. Large or persistent warts may be cleared by curettage and cautery. Recurrences are possible.

 

Viral warts
Occasionally, warts pose a diagnostic problem if they are unusually large or have unusual features. This patient presented with a warty lesion on his toe that had grown for four years, despite treatment with wart paints. Thinking it infected, his GP prescribed flucloxacillin, which was ineffective. The patient was referred to a dermatologist and biopsy confirmed it to be a viral warty naevus.

Topical imiquimod led to improvement.

 

Hand, foot and mouth disease
Hand, foot and mouth disease usually affects young children. Its incubation period is three to five days and it commonly also affects others in contact with the patient. The patient might develop low-grade fever; a rash on the hands and feet, of small, oval flat vesicles surrounded by erythema; and blisters and ulcers in the mouth.

Cold, soft foods, antiseptic mouth washes and paracetamol can be recommended. The condition should subside spontaneously within a few days. No exclusion from school is required.

 

Scabies
In patients with scabies, a female mite burrows into the skin and lays its eggs. The patient develops hypersensitivity reaction with erythematous, itchy, papular rash, and linear burrows on the trunk and limbs. Burrows can often be seen on the insteps and backs of the heels, the wrists and buttocks, and between the fingers. Scratching often encourages secondary infection and impetiginous change.

Close contacts should be treated alongside the patient, with malathion or permethrin cream or lotion applied to the whole body and repeated a week later. Patients should be excluded from school until treated.

 

Cutaneous larva migrans
Cutaneous larva migrans is caused by parasitic larvae of hookworm, which infests dogs and cats. Humans walking barefoot can become infected from animal faeces. The foot is most likely to be affected. In humans, the infestation is limited to the dermis.

Raised, itchy, snake-like tracks appear emanating from the larva point of entry and advance daily, until the larvae die four to eight weeks later. The problem is therefore self-limiting, although widespread lesions can be treated with an anthelmintic such as ivermectin, albendazole or tiabendazole (available on a named-patient basis).

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