Dermal-binding linear IgA disease: an uncommon subset of a rare immunobullous disease.

BACKGROUND

Linear IgA disease (LAD) is an acquired subepidermal blistering disorder, characterized clinically by urticated plaques, papules, vesicles and bullae. Scarring is not usually observed. Direct immunofluorescence on clinically uninvolved skin shows linear deposition of IgA at the basement membrane zone (BMZ). Indirect immunofluorescence on salt-split skin shows dermal binding in a minority of cases.

AIM

To identify and characterize patients with LAD who have IgA anti-BMZ autoantibodies directed against the dermal side of salt-split human skin (dermal-binding autoantibodies).

METHODS

This was a retrospective study of patients with a diagnosis of LAD referred to the dermatology department in Oxford between 1986 and 2004, who demonstrated dermal-binding circulating IgA autoantibodies on indirect immunofluorescence. Clinical features were reviewed and target antigens identified by immunoblotting.

RESULTS

In total, 17 of 101 patients with LAD were found to have dermal-binding autoantibodies. This subset of LAD was relatively more common in adults than in children. There were no other clinical features that distinguished these patients from others with LAD. Collagen VII, the target antigen in epidermolysis bullosa acquisita (EBA), was identified in two of our cohort, but none of the classic clinical features of mechanobullous EBA was observed.

CONCLUSION

This is the largest cohort of patients with dermal-binding LAD to date. Our patients were clinically indistinguishable from those with non dermal-binding LAD, and showed no evidence of the classic mechanobullous EBA phenotype.