Chapter 160 Dermatitis Herpetiformis
• Pruritic papulovesicular eruption, usually on the extensor surfaces
• Most common in middle-aged white males but may be seen in individuals of any age
• IgA deposits in the dermal papillae; confirmed by immunofluorescence
• Asymptomatic celiac disease (gluten-sensitive enteropathy) in 75% to 90% of patients
Dermatitis herpetiformis (DH) is a cutaneous manifestation of gluten-sensitive enteropathy (celiac disease). Patients with DH demonstrate serum IgA antibodies against epidermal transglutaminase and tissue transglutaminase.1 The putative autoantigen of DH is epidermal transglutaminase. DH has been referred to as “celiac disease of the skin.”2 Just as in celiac disease (CD), a gluten-free diet is most often all that is required to resolve the lesions. Absorption studies (see Chapter 20) can be used to assess the degree of enteropathy.
Most individuals with CD have celiac-associated antibodies and specific pairs of allelic variants in two HLA genes, HLA-DQA1 and HLA-DQB1.3 Only 3% of individuals with one or both of these alleles develops CD, yet 30% of the general population has one of them. Therefore, their presence is not diagnostic of CD but their absence excludes a diagnosis of CD. Genetic testing is available for the assessment of CD.
The average age at onset of DH is 7.2 years; it has a predilection for the elbows, knees, and buttocks. Skin biopsy shows granular or fibrillar IgA deposits.4 The characteristic skin lesions found in patients with DH are extremely itchy grouped vesicles most frequently located on extensor surfaces. Intense pruritus is the predominate symptom; however, DH is a clinical chameleon and can present with excoriations, eczematous lesions, or minimal patterns of discrete erythema or digital purpura.5
The most important factor in the treatment of patients with DH is the elimination of all sources of gluten. Frazer’s criteria for the diagnosis of gluten-sensitive enteropathy (improvement on a gluten-free diet and relapse after reintroduction) have been used in many studies and have shown conclusively that the rash and villous atrophy of DH are largely gluten dependent.6–11 Gluten elimination results in improvement in virtually all patients, including elimination of the reticulin and gluten antibodies found in patients with DH.2,12
Further study of the wheat connection has shown that the gliadin polypeptide of gluten is most likely the key antigen. Indirect immunofluorescence shows antibodies to gliadin in the sera of 45% of patients with DH. The titer and correlation increase with increasing severity of the disease; 81% of patients with severe jejunal abnormalities show antibodies to gliadin.13
Despite the published benefits of a gluten-free diet in the treatment of DH for more than 30 years now, this treatment is still often omitted from conventional dermatology and medical textbooks. The advantage of a gluten-free diet over drugs like dapsone (the most widely prescribed drug for DH) is obvious, as this drug is often associated with severe side effects. With the gluten-free diet, on the other hand:
• Most patients (more than 65%) experience complete resolution and the rest improve substantially.
• There is complete resolution of the enteropathy associated with DH.
• Harsh medications can be eliminated or substantially reduced.