Author: Dr Ian Coulson, Consultant Dermatologist and Editor-in-Chief, 2022.
Edited by the DermNet content department
This 46-year-old man has itchy lesions symmetrically on his elbows and knees, sacrum, scalp, and beard area. The lesions started six months ago and topical steroids have been of little help in reducing the itch. There is a family history of atopic eczema, although he has never had any atopic symptoms.
Routine blood tests (ie, full blood count, renal and liver function) are all normal.
This man has dermatitis herpetiformis. This is an immunobullous disorder associated with gluten sensitivity. The vesicles and blisters that arise in this condition are small (2 to 4 mm) and because the condition is so itchy, they are often excoriated so that intact blisters are seen only infrequently.
The clue to the diagnosis is often from the rash distribution. It affects symmetrically the elbows and knees, sacrum, interscapular area, scalp, and beard area. Itch is usually severe. It is slightly more common in atopic individuals.
The diagnostic test is direct immunofluorescence from a perilesional skin biopsy. Granular IgA deposits are seen at the dermo-epidermal junction. It is positive in 80% of sufferers on the first biopsy, 95% with the second biopsy, and close to 100% on the third biopsy so repeat investigation may be needed if clinical suspicion persists. Coeliac serology may be positive.
Gluten-sensitive enteropathy is always present but may be asymptomatic and may be unassociated with biochemical evidence of malabsorption. However, iron or folic acid deficiency may be identified. There is a known association with haemochromatosis.
Treatment requires a rigorous gluten-free diet; this may take two years to be fully effective. It can reduce the incidence of small-bowel lymphoma that can complicate the enteropathy. Oral dapsone usually results in the welcome and rapid relief of itch. The dose can be reduced to the lowest that maintains symptom relief.
