Pictorial case study: Itchy rash

The case: Mrs M had been in a care home for a month when she began to complain of an itchy rash on her abdomen and thighs. Examination revealed a non-specific rash with marked excoriations caused by repeated scratching.

The patient presented with a non-specific rash with excoriations (Author image)
The patient presented with a non-specific rash with excoriations (Author image)

A diagnosis of eczema was made and an antihistamine and topical corticosteroid was prescribed to alleviate the itching. Advice about emollient use was also given.

However, there was no improvement and other patients in the home also complained of itching.

A further examination of the patient found evidence of a few 'burrows'.

Diagnosis and management
The contents of a burrow was viewed under the microscope and a scabies mite could be seen. Scabies is caused by Sarcoptes scabiei, a parasite which burrows into the epidermis to lay eggs. Transmission is by skin-to-skin contact with an infected person. Scabies can also be sexually transmitted. Symptoms develop several weeks after contact when the patient develops an allergic reaction to the faeces of the mite. Patients present with an itchy urticarial rash or papules and vesicles. Nodules on the shaft of the penis are typical of scabies.

Scabies can affect any part of the body apart from the scalp. It is common on the wrists, axilla or between fingers. It is often misdiagnosed as eczema. Complications include eczematisation of the skin and secondary infection.

Diagnosis is clinical if burrows can be found and should be confirmed microscopically or with a dermatoscope. Treat with permethrin 5%. Apply cream to the whole body, including face and scalp and leave for eight hours before washing off. Treatment is repeated after seven days. Malathion 0.5% may be needed if the patient is intolerant to permethrin. Malathion should be washed off after 24 hours, and repeated after seven days.

Severe or persistent cases should be discussed with a dermatologist. Itching is relieved with crotamiton lotion, topical corticosteroids and/or oral antihistamine.

Possible differential diagnoses

  • Eczema.
  • Urticaria.
  • Flea bites.
  • Psoriasis (crusted scabies).
  • Drug reactions.

Differential diagnosis
Flea bites

  • Commonest flea in the UK is the cat and dog flea (ctenocephalides).
  • Flea bites present with clusters of itchy, inflammatory papules
  • especially in flexures.
  • Can cause urticarial reaction to the bites.
  • Advise not to scratch and use antiseptic soap to discourage secondary
  • infection.
  • Topical calamine lotion or corticosteroid to ease the itching.
  • Antibiotic if secondary infection occurs.
  • Vacuum carpets, soft furnishings and spray with an insecticide.

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