Elevation of IgA anti-epidermal transglutaminase antibodies in dermatitis herpetiformis

Summary Background Dermatitis herpetiformis (DH) is a papulovesicular eruption caused by ingestion of gluten. It is characterized by the deposition of IgA in the dermal papillae. IgA antibodies directed at tissue transglutaminase (TG2) are elevated in gluten‐sensitive diseases including DH and coeliac disease (CD). More recently, antibodies directed at epidermal transglutaminase (TG3) were identified in patients with DH, and this may be the dominant autoantigen in this disease. Objectives To measure IgA antibodies to TG3 and TG2 in patients with DH and CD, and control populations. Methods Serum IgA antibodies against TG2 and TG3 were measured from adults with DH, adults and children with CD, patients with psoriasis, adult Red Cross blood donors, and paediatric controls. Results Patients with DH and CD had elevated levels of IgA anti‐TG2 antibodies compared with control populations. The levels in the patients with DH and adults with CD were similar. IgA anti‐TG2 antibodies were higher in the children with CD compared with adults with DH and CD, and with control populations. Patients with DH and adults with CD had elevated levels of IgA anti‐TG3 antibodies compared with children with CD and control populations. There was a trend towards higher levels in the patients with DH compared with adults with CD. Conclusions IgA antibodies to TG3 are elevated in patients with DH and adults with CD. The progressive expansion of the epitope‐binding profile of IgA antitransglutaminase antibodies in patients with CD may explain the development of DH in patients with undiagnosed CD during their adult life.