Pictorial case study - Scabies

A rash after respite care was found to be caused by scabies. By Dr Jean Watkins

Presentation

A family had returned from holiday and collected their grandmother from respite care. About four weeks later, the grandmother developed a very itchy, widespread, erythematous, vesicular rash.

On examination, the GP found a small, greyish, serpiginous, linear lesion with a minute black speck at the closed end, in an interdigital web space. He assumed it to be a burrow and was suspicious of a diagnosis of scabies. A scraping was taken from the burrow and, under the microscope, the finding of a mite and eggs confirmed the diagnosis.

Management

A diagnosis of scabies is made on clinical grounds, history of contacts and, in about 50% of cases, confirmed by microscopy of scrapings from a burrow. Another clue may be firm red nodules found elsewhere, such as the axillae or elbows.

Treatment is two applications, a week apart, of 5% permethrin cream to the whole body, washed off after eight to 12 hours.

This should clear the condition, but only if all household members and other close contacts are treated at the same time, so the mites are not recirculated. An alternative treatment to permethrin is malathion.

In this case, it is likely the infestation was acquired while the patient was in the care home. The home should be notified so that all residents and carers can be treated as well. The Health Protection Agency should be contacted to supervise the operation.

Specialist advice may be required for those patients under the age of two years or those not responding to treatment. Severe or stubborn cases may be offered oral ivermectin on a named patient basis.

Topical crotamiton, with a sedating antihistamine at night, may help to relieve itching, if necessary.

In cases of secondary infection, an antibiotic should be considered. Should sexual contact be suspected, the patient should be reviewed at a GUM clinic to exclude the possibility of other STIs.

Differential diagnoses

  • Insect bites
  • Psoriasis
  • Eczemal
  • Urticaria

Dr Watkins is a retired GP in Hampshire

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