Dermatitis herpetiformis is an autoimmune blistering disease, which can involve a younger subset of patients when compared to pemphigus vulgaris and bullous pemphigoid. The typical age of onset is between 30 and 40 years of age, with men more affected than women. A genetic predilection is found in families and associated HLA-DQ2 and HLA-DQ8.
Dermatitis herpetiformis is linked to celiac disease and dietary gluten. Both celiac disease and dermatitis herpetiformis have gluten-sensitive enteropathy. IgA autoantibodies are found in both conditions. In dermatitis herpetiformis, epidermal transglutaminase is the main antigen.7 In celiac disease, the main antigen is tissue transglutaminase. In the skin, transglutaminase is found in the dermal capillaries and the basal cells of the epidermis. Transglutaminase is a cytoplasmic calcium-dependent enzyme that catalyzes crosslinks between glutamine and lysine. Transglutaminase modifies the gliadin portion of gluten and make it an autoantigen. Protein to protein crosslinking between transglutaminase and gliadin complexes causes an intense autoantibody response. Due to the inflammation in the skin, a blister is formed in the basement membrane zone between the epidermis and dermis.
The patient will usually present with excoriations and complaints of intense pruritus and may have gastrointestinal symptoms such as diarrhea and abdominal cramping.
Because the blister is forming between the dermis and the epidermis, it should be a tense blister. However, since this condition is so pruritic, most patients will have scratched the blister off leaving only erosions and excoriations (Figure 22-8). The eruption is classically symmetric with a distribution on the extensor surfaces of the extremities, elbows, knees, buttocks, scalp, and neck. Face and groin may also be involved, but rarely the mucosa.
Dermatitis herpetiformis. Excoriated erosions on elbow and forearm.
Histopathology of a skin biopsy of an intact blister/vesicle (if it can be found) will show a subepidermal blister with neutrophils and some eosinophils in the tips of the dermal papillae (Figure 22-9).8
A biopsy of perilesional skin for immunofluorescence will show granular deposits of IgA at the tips of the dermal papillae (Figure 22-10).
Indirect immunofluorescence of the blood for antiendomysial antibodies is specific for dermatitis herpetiformis.
Histopathology of dermatitis herpetiformis. Subepidermal blister with neutrophils and eosinophils in the tips of the dermal papillae.
Direct immunofluorescence microscopy of perilesional skin in dermatitis herpetiformis. Granular deposits of IgA at the tips of the dermal papillae.
A total IgA level should be done before any other serological tests as selective IgA deficiency is more common in celiac patients with celiac disease and needs to be considered in the evaluation of patients with dermatitis herpetiformis. ELISA for IgA antitissue transglutaminase is available. Studies are reviewing the ELISA for IgA antiepidermal transglutaminase and this may become a very useful tool.
The key diagnostic features of dermatitis herpetiformis are erosions and excoriated papules on the extensor surfaces of the extremities, elbows, knees, buttocks, scalp, and neck.
✓ Scabies: Pruritic papules on elbows, knees, body folds, volar wrists, and finger web spaces. Scabies mite are often seen in skin scrapings.
✓ Bullous pemphigoid: Tense bullae in a bilateral symmetric distribution.
✓ Other: Linear IgA bullous dermatosis, atopic dermatitis, and urticaria.
A strict gluten free diet is a mainstay of therapy and consultation with a dietician is important as this diet is difficult to maintain. Even with a strict gluten free diet, the skin lesions are slow to respond.9 Dapsone and sulfapyridine rapidly control the skin lesions.8 Systemic corticosteroids are not helpful in this disease. Antihistamines may help with pruritus.
Dermatitis herpetiformis is associated with other immune-mediated conditions and screening studies for thyroid disease, diabetes, and connective tissue disease should be considered.7,10 If clinical signs of gastrointestinal disease or non-Hodgkin lymphoma are present, a work-up must be done as these diseases are associated with dermatitis herpetiformis. Patients with gastrointestinal disease are at risk for splenic atrophy and a blood smear should be done to detect Howell-Jolly bodies and other abnormalities.
Indications for Consultation
Dermatitis herpetiformis is a complex blistering disorder that can be difficult to diagnosis. Patients should be referred to dermatology for diagnosis and management.
Celiac Disease Foundation: www.celiac.org