Dermatitis herpetiformis (DH) is a chronic skin condition with a characteristic pattern of lesions, with intense itching and burning sensations.
Genetic factors, the immune system, and a sensitivity to gluten play a role in this disorder. The precise details remain unknown.
DH is not uncommon. It affects males and females equally and occurs in about 1:100,000 people. It is more common in Caucasians than Blacks, and rare in the Japanese population. Onset is most frequently in the late second to the fourth decades of life.
A new unscratched lesion is red, raised, and usually less than 1 cm in diameter with a tiny blister at the centre. However, if scratched, crusting appears on the surface. The ‘burning” or “stinging” sensation is different from a “regular” itch, and can often occur 8-12 hours before a lesion appears.
The most common areas are the elbows, knees, back of the neck, scalp, the upper back, and the buttocks. Facial and hair-line lesions are not uncommon; the inside of the mouth is rarely affected. The rash has symmetric distribution.
Dermatitis herpetiformis is only diagnosed and confirmed by a dermatologist obtaining a slight skin biopsy from uninvolved skin adjacent to blisters or erosions. Other forms of dermatitis can mimic dermatitis herpetiformis necessitating skin biopsy for correct diagnosis.
Small bowel biopsies will confirm a diagnosis of coexisting celiac disease but are not essential if the skin biopsy confirms the diagnosis of dermatitis herpetiformis. Referral to a gastroenterologist may be necessary for assessing the extent of the underlying intestinal injury and associated deficiencies of iron, calcium and vitamins.
The skin symptoms usually predominate over intestinal symptoms. Blood tests for celiac disease may be negative, reflecting the absence or paucity of intestinal symptoms expected when there is milder, more patchy villous atrophy seen on small bowel biopsies.
Treatment is by drugs, and diet restrictions.
Drugs: Dapsone (Avlosulfon) or related sulphones: The response is dramatic. Within 24-48 hours the burning is relieved and the rash starts to disappear. The aim is to use the smallest dose possible to keep the itch and rash under control. It has no effect on the gut abnormality.
Diet: Gluten-free Diet: Elimination of all wheat, rye, barley, oats, triticale, and any parts thereof from the diet will result in:
- the skin lesions improving
- the gut returning to normal
- a substantial reduction in or the elimination of the need for sulphones to control the skin rash
- a decreased risk of malignancy