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.Dermatitis herpetiformis was first described by Louis Adolphus Duhring in 1884. A connection between DH and coeliac disease was recognized in 1967. Signs and symptoms
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). : 616   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.
Class A antibodies (IgA) deposit in the gut. Some may bind to the CD89 (FcαRI) receptor on macrophages (M1) via their Fc region (constant region). This will trigger endocytosis of the tTG-IgA complex, resulting in the activation of macrophages. Macrophages secrete more IL-8, propagating the neutrophil-mediated inflammatory response. The purportedly cross-reactive autoantibodies may migrate to the skin in dermatitis herpetiformis. IgA deposits may form if the antibodies cross-react with epidermal transglutanimase (eTG). Some patients have eTG-specific antibodies instead of tTG-specific cross-reactive antibodies and the relationship between dermatitis herpetiformis and celiac disease in these patients is not fully understood. Macrophages may be stimulated to secrete IL-8 by the same process as is seen in the gut, causing neutrophils to accumulate at sites of high eTG concentrations in the dermal papillae of the skin. Neutrophils produce pus in the dermal papillae, generating characteristic blisters. IL-31 accumulation at the blisters may intensify itching sensations. Memory B and T cells may become activated in the absence of PAMPs and DAMPs during successive encounters with tTG-modified gliadin complexes or modified gliadin alone, respectively. Symptoms of dermatitis herpetiformis are often resolved if patients avoid a gluten-rich diet. Diagnosis
Dermatitis herpetiformis often is misdiagnosed, being confused with drug eruptions, contact dermatitis, dishydrotic eczema (dyshidrosis), and even scabies. Other diagnoses in the differential diagnosis include bug bites and other blistering conditions such as bullous pemphigoid, linear IgA bullous dermatosis, and bullous systemic lupus erythematosus.