Dermatitis herpetiformis (DH) is a chronic autoimmune blistering skin condition, characterised by intensely itchy blisters filled with a watery fluid. DH is a cutaneous manifestation of coeliac disease, although the exact causal mechanism is not known. DH is neither related to nor caused by herpes virus; the name means that it is a skin inflammation having an appearance (Latin: -formis) similar to herpes.
The age of onset is usually about 15–40, but DH also may affect children and the elderly. Men are slightly more affected than women. Estimates of DH prevalence vary from 1 in 400 to 1 in 10,000. It is most common in patients of northern European and northern Indian ancestry, and is associated with the human leukocyte antigen (HLA) haplotype HLA-DQ2 or HLA-DQ8 along with coeliac disease and gluten sensitivity.
Signs and symptoms
Its characteristic rash resembles herpes and is the basis of its clinical name
Dermatitis herpetiformis is characterized by intensely itchy, chronic papulovesicular eruptions, usually distributed symmetrically on extensor surfaces (buttocks, back of neck, scalp, elbows, knees, back, hairline, groin, or face). The blisters vary in size from very small up to 1 cm across. The condition is extremely itchy, and the desire to scratch may be overwhelming. This sometimes causes the affected person to scratch the blisters off before they are examined by a physician. Intense itching or burning sensations are sometimes felt before the blisters appear in a particular area.
The signs and symptoms of DH typically appear around 30 to 40 years of age, although all ages may be affected. Although the first signs and symptoms of dermatitis herpetiformis are intense itching and burning, the first visible signs are the small papules or vesicles that usually look like red bumps or blisters. The rash rarely occurs on other mucous membranes, excepting the mouth or lips. The symptoms range in severity from mild to serious, but they are likely to disappear if gluten ingestion is avoided and appropriate treatment is administered.
Dermatitis herpetiformis symptoms are chronic, and they tend to come and go, mostly in short periods of time in response to the amount of gluten ingested. Sometimes, these symptoms may be accompanied by symptoms of coeliac disease, which typically include abdominal pain, bloating or loose stool, weight loss, and fatigue. However, individuals with DH often have no gastrointestinal symptoms even if they have associated intestinal damage.
The rash caused by dermatitis herpetiformis forms and disappears in three stages. In the first stage, the patient may notice a slight discoloration of the skin at the site where the lesions appear. In the next stage, the skin lesions transform into obvious vesicles and papules that are likely to occur in groups. Healing of the lesions is the last stage of the development of the symptoms, usually characterized by a change in the skin color. This may result in areas of the skin turning darker or lighter than the color of the skin on the rest of the body. Because of the intense itching, patients usually scratch, which may lead to the formation of crusts.
A strict gluten-free diet must be followed, and usually, this treatment will be a lifelong requirement. Avoidance of gluten will reduce any associated intestinal damage and the risk of other complications. It can be very difficult to maintain a strict gluten-free diet, however, as contamination with gluten is common in many supposedly gluten-free foods and restaurants.
Dapsone is an effective initial treatment in most people and is the initial drug of choice to alleviate the rash and itching. Itching is typically reduced within 2–3 days, however, dapsone treatment has no effect on any intestinal damage that might be present. After some time on a gluten-free diet, the dosage of dapsone usually may be reduced or even stopped, although this may take many years. Dapsone is an antibacterial, and its role in the treatment of DH, which is not caused by bacteria, is poorly understood. It may cause adverse effects, especially hemolytic anemia, so regular blood monitoring is required.