Granular deposits of IgA represent the specific cutaneous marker of dermatitis herpetiformis. The prevalence of IgA deposits in the skin of patients with coeliac disease without dermatitis herpetiformis remains unknown. In this prospective case-control study, skin biopsies from newly diagnosed coeliac patients without dermatitis herpetiformis were analysed by direct immunofluorescence. Controls included healthy volunteers and patients with both bowel symptoms and skin eruptions unrelated to coeliac disease. Clinical data and serum level of anti-tissue transglutaminase and anti-epidermal transglutaminase IgA antibodies were collected from patients and controls. Granular deposits of IgA or IgA1 in the skin were found in 29 out of 45 patients with coeliac disease (64.4%), and in none of the included controls (specificity 100%; sensitivity 64.4%). Positive direct immunofluorescence correlated significantly with an increased serum level of anti-epidermal transglutaminase IgA antibodies (p < 0.005). This study shows that granular deposits of IgA represent a low sensitive, but highly specific, cutaneous marker of coeliac disease independent of dermatitis herpetiformis.
Keywords: coeliac disease; dermatitis herpetiformis; direct immunofluorescence; epidermal transglutaminase; gastroenterology; granular deposit; immunoglobulin A; general dermatology.