Dermatitis herpetiformis
Definition
Dermatitis herpetiformis (DH) is characterised by a persistent, itchy blistering
skin rash which usually occurs on the knees, elbows, buttocks and back, although can affect any area of skin. DH results from gluten sensitivity and intestinal biopsy nearly always shows the characteristic flattening of intestinal villi. However, unlike
coeliac disease itself, the gastrointestinal symptoms may be mild and are often not apparent at all; less than 10% of people with DH have gastrointestinal symptoms characteristic of
coeliac disease. All patients with DH have some degree of coeliac disease, and are very likely to reflect the entire spectrum of histologic and clinical coeliac disease in adults.
Prevalence
DH is less common than coeliac disease with a UK incidence of about 1 in 10,000. It is slightly more common in men than women (ratio of 3:2) and most commonly appears between the ages of 15-40 years; it is rare in children. DH is much less common in black and Asian populations. As with
coeliac disease, there is an inherited tendency to develop the disease, and there are links with auto-immune thyroid disease and
Type 1 diabetes with both patients with DH and family members being at increased risk of developing these disorders. The prevalence of HLA-DQ2 and -DQ8 is the same as in coeliac disease, supporting the concept that DH is a manifestation of coeliac disease.
Diagnosis
Patients with DH demonstrate intensely pruritic papulovesicles and excoriations on the elbows, knees, buttocks, and scalp. Cases rarely present without characteristic involvement of one of these areas. According to a recent report granular IgA must be present in dermal papillary tips in perilesional
skin for a definite diagnosis.
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