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DERMATITIS HERPETIFORMIS

Dermatitis Herpetiformis (DH) is a very itchy, autoimmune skin blistering disorder. It was once regarded as a classic autoimmune blistering skin disease. However, mounting evidence against such a view suggests that dermatitis herpetiformis is an allergic skin reaction to gluten, a protein found in wheat and other food grains. Dermatitis herpetiformis usually occurs in young adults and it is a lifelong condition, with chances of remission in only 10% to 20% patients. It is a very difficult disease to cope with, since young people tend to rebel against a life-long gluten free diet that deprives them of foods like bread and cakes.

Dermatitis Herpetiformis Symptoms

Symptoms are burning, stinging and itching around the elbows, knees, scalp, buttocks and back. Dermatitis herpetiformis can spread to more sites and the severity can vary from person to person and over time in the same person. The watery blisters are not permanent and may be scratched away. But new blisters reappear.

Clinical and pathological features

On the skin, there are commonly erythema, urticarial plaques, papules, herpetiform vesicles, and excoriations, but large blisters are rare.

Some of the unique features of dermatitis herpetiformis are a strong association with gluten-sensitive enteropathy (GSE) or celiac disease (spelt coeliac disease in Europe), affecting the guts; association with iodine; and a common association with autoimmune thyroid disease and rarely with other autoimmune diseases. It has a characteristic pattern of skin signs involving the elbows, knees and buttocks. It is usually a life long disease with frequent remissions and relapses. Remissions occur with a strict and long lasting gluten-free diet and relapses occur with gluten containing diets. There is improvement under UV light exposure, suggesting seasonal variations in severity can be involved.

Allergies are usually initiated by the body’s IgE (immunoglobulin type E antibody) production system. In dermatitis herpetiformis, however, the allergy is triggered by the antibody IgA present in the body. This makes standard allergy treatments, which mostly target IgE type allergic responses, ineffective. Dermatitis herpetiformis is caused when IgA antibodies precipitate in the papillary skin dermis, triggering an autoimmune response in the skin. Recently, epidermal transglutaminase (TGe) has been identified as the main antigen target of these IgA precipitates, an enzyme, hitherto undetected. Although IgA deposition is crucial for disease development, an increased serum IgA is not necessary for pathogenesis. There are even case reports of dermatitis herpetiformis occuring in patients with a partial IgA deficiency.

Role of gluten

One theory says that dermatitis herpetiformis is an immunologic response to chronic stimulation of the gut by dietary gluten. Gluten combines with IgA and with help of iodine produces inflammation – first and foremost in the stomach. Though we all need iodine for our general health dermatitis herpetiformis patients generally avoid iodized salts (iodine is artificially added to many common brands of salt) and get their iodine from other natural sources in their diet.

Almost 90% of dermatitis herpetiformis patients have an associated GSE or celiac disease. About 15% to 25% of patients with celiac disease develop dermatitis herpetiformis. Cases of severe celiac diseases are never associated with a skin rash. It is the latent and silent forms of GSE, occurring without major clinical signs, which are associated with this skin disease. It is this skin disease which usually signals a probable GSE.

The critical role of GSE in dermatitis herpetiformis development is confirmed by relapses due to resumption of glutinous diets. However, there are exceptions in case of people with spontaneous remissions of skin symptoms.

One major argument for a strict gluten-free diet in dermatitis herpetiformis would be to prevent the development of cancerous conditions which occur significantly more in dermatitis herpetiformis and contact dermatitis patients who don’t control their diets.

Immune complexes

It has long been argued that dermatitis herpetiformis is an immune complex disease due to the presence of dermatitis herpetiformis bodies in the papillary dermis and the absence of IgA circulating antibodies binding to the skin. The detection of IgA immune complexes in the symptom-free and damage-free kidneys of dermatitis herpetiformis patients supports this view. It further supports the hypothesis that IgA immune complexes circulate and can get stuck in different organs.

Genetics

The leading theory is that genetic predisposition for gluten sensitivity, coupled with a diet high in gluten, leads to dermatitis herpetiformis. Patients with dermatitis herpetiformis have a clear genetic background as indicated by the fact that 10% to 15% of their first-degree relatives also have dermatitis herpetiformis or celiac disease. All patients with gluten sensitivity, affecting the skin, have the same sets of genes. Gluten sensitivity is considered as a multifactorial and polygenic disease with possibly more susceptible zones. Monozygous twin studies, showing concordance for gluten sensitivity in the majority but not all the sib-pairs, suggesting that environmental as well as other genetic factors also determine the phenotype.

Some individuals, with a distinct genetic background, tend to lose the oral tolerance to gluten. Depending on how the immunological system and environmental factors interact, these individuals might develop either a mild to severe gluten-induced enteropathy or a mild gluten induced enteropathy with skin disease.

Conclusion

The task before researchers now is to determine whether the skin rash in dermatitis herpetiformis is a classic autoimmune blistering skin disease or whether it has an immune complex basis. The latter alternative seems most likely, though it has not been proven clearly.