Dermatitis herpetiformis (DH) may occur at any age but patients typically present in the 2nd to 4th decades of life. It is twice as common in males. Most patients have an associated asymptomatic gluten sensitive enteropathy that may be demonstrated by small bowel biopsy.
Clinically, patients present with single or grouped vesicles, papules, or urticarial plaques. Lesions are typically distributed symmetrically on extensor surfaces with involvement of the elbows, knees, buttocks, shoulders, and sacral areas most commonly. Many also have involvement of the scalp, posterior nuchal area, face, and/or facial hairline. Mucous membranes are typically spared. Patients usually experience severe burning and itching. These symptoms often precede the appearance of skin lesions by 8 to 12 hours. In addition, signs and symptoms such as steatorrhea, abnormal D-xylose absorption, iron or folate deficiency anemia due to malabsorption, achlorhydira, atrophic gastritis, and pernicious anemia as a result of gluten sensitive enteropathy may occur.
On electron microscopic exam, blister formation is in the lamina lucida. Histopathologic exam is characterized by collections of neutrophils in the dermal papillae forming microabscesses. Eosinophils and dermal edema leading to subepidermal separation are also typically present. Direct immunofluorescence of normal appearing or perilesional skin demonstrates granular IgA deposits in the papillary tips. Complement components may be seen as well. Indirect immunofluorescence for circulating anti-basement membrane zone antibodies is usually negative. However, circulating IgA antiendomysium antibodies that bind to the intermyofibril substance of smooth muscle may be detected and these correlate with the severity of the associated intestinal disease. These antibodies can also be used to monitor whether or not patients are adhering to their gluten-free diet. In addition, it has recently been shown with ELISA that DH patients have circulating IgA autoantibodies to tissue transglutaminase which is the autoantigen of IgA anti-endomysium antibodies in celiac disease. These antibodies reflect the extent of gastrointestinal involvement in DH patients and the levels correlate with titers of IgA anti-endomysium antibodies. Antireticulin and antigliadin antibodies are detected in two thirds of DH patients but they are not disease specific and do not correlate with disease severity.
Patients with DH have an increased frequency of gastrointestinal lymphomas as well as a higher incidence of other autoimmune disorders. NSAIDs and oral iodides may exacerbate this condition. The course is indefinite although the degree of disease severity may vary with time.