Dermatitis herpetiformis

What is it?

Dermatitis herpetiformisUsually shortened to DH, this is a form of coeliac disease where the skin is affected with small blisters. (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 the skin (1).

Prevalence

DH is less common than coeliac diseaseA condition where a person is unable to eat gluten as it makes their body attack itself. with a UK incidence of about 1 in 10,000. It is more common in men than women (ratio of 3:2) and most commonly appears between the ages of 15-40 years.

As with coeliac disease, DH has a genetic link. There are also links with autoimmuneA reaction to a trigger which causes the body to attack itself. thyroid disease and Type 1 diabetes (2) in patients who have coeliac disease and DH. Those with DH, and their family members, may have increased risk of developing these disorders (3).

The prevalence of HLA-DQ2 and -DQ8 is the same as in coeliac disease, supporting DH as a manifestation of coeliac disease (4).

Diagnosis of DH

DH is diagnosed by a skin biopsyA dermatologist takes a small sample of skin from an area that is unaffected by the DH. . Biopsy needs to be performed on uninvolved skin (clinically normal-appearing skin immediately next to an area of inflammation). False negatives may occur if a biopsy is performed on skin that is affected by the condition.

IgA antibodiesExist in the blood and are used by the immune system to attack viruses or bacteria. must be present in the skin biopsy for a definite diagnosis (4). It is important the person continues to eat glutenA protein that is found in the cereals wheat, barley and rye. as the gluten-freeWhen a food has less than 20 parts per million (ppm) of gluten so it is safe for people with coeliac disease to eat. diet can cause false negative results.

Diagnosis of coeliac disease

It is likely that all patients with DH have some degree of coeliac disease. The serological and immunological presentations of coeliac disease are also found in people diagnosed with DH.

The NICENational Institute for Health and Clinical Excellence - an independent organisation responsible for providing national guidance on promoting good health and preventing and treating ill health. NICE had produced a clinical guideline on the recognition and assessment of coeliac disease. guideline on the recognition and diagnosis of coeliac disease recommends that people with DH should be screened for coeliac disease. The gastrointestinal symptoms of coeliac disease can be mild and in some cases are not apparent at all. Less than 10% of people with DH have gastrointestinal symptoms characteristic of coeliac disease (1).

Clinically, 10-20% of patients with DH present with classic symptoms of malabsorption and another 20% are estimated to have atypical symptoms, but at least 60% of patients have 'silent' coeliac disease.

The presence of DH is a marker of coeliac disease that is independent of the severity of histologic coeliac disease or the intestinal symptoms.

Management

DH is managed by a gluten-free diet and drug treatment. Once established on a gluten-free diet it can often take several months before the rash improves and nearly two years before it disappears completely. Both the skin disease and the intestinal disease return with the reintroduction of gluten to the diet.

Drugs, such as Dapsone (Diaminodiphenylsulfone), are important for managing DH. The skin symptoms in DH clear rapidly on treatment with Dapsone and can reappear rapidly if Dapsone is discontinued. Side effects of Dapsone include haemolytic anaemic, neuropathy, depression and headache.

Dapsone has no influence on intestinal abnormality. It is important to continue a gluten-free diet along side drug treatment.

Long term consequences

Many of the long-term implications of coeliac disease are also relevant to patients with DH, including lymphoma (5). Thyroid abnormalities can occur in 15-20% of people with DH (6).

Coeliac UK has an information sheet for people with dermatitis herpetiformis. This is available in the Members area of the website.

References

1.Caproni M, Anigga E, Melani L, et al (2009) Guidelines for the diagnosis and treatment of dermatitis herpetiformis. European Ac of Dermatology and Venerology. 23: 633-638.

2 Reunala T & Collin P (1997) Diseases associated with dermatitis herpetiformis. British Journal of Dermatology. 136(3): 315-8.

3 Hervonen K, Viljamaa M, Collin P, et al (2004) The occurrence of type 1 diabetes in patients with dermatitis herpetiformis and their first degree relatives. British Journal of Dermatology. 150(1): 136-138.

4 Zone JJ (2005) Skin manifestations of Celiac Disease. Gastroenterology. 128: S87-S91.