IgA-mediated epidermolysis bullosa acquisita: two cases and review of the literature.

We describe 2 adult patients with a subepidermal bullous dermatosis with exclusively linear IgA depositions along the epidermal basement membrane zone that were deposited in the sublamina densa zone as witnessed by direct immunoelectron microscopy. Indirect immunofluorescence microscopy of patients' sera revealed circulating IgA autoantibodies that bound exclusively to the dermal site of salt-split skin substrate. Immunoblot analysis using dermal and keratinocyte extracts were negative. Indirect immunofluorescence microscopy using type VII collagen-deficient skin ("knockout" substrate) showed no IgA binding, whereas linear IgA binding was seen at the epidermal basement membrane zone in normal human skin. The autoantigen in the patients was thus type VII collagen. A diagnosis of IgA-mediated epidermolysis bullosa acquisita (IgA-EBA) was made. We systematically reviewed the literature of this subset of patients with linear IgA dermatosis on the basis of the following criteria: exclusive binding of serum-IgA to the dermal side of salt-split skin or IgA depositions in the sublamina densa zone by indirect or direct immunoelectron microscopy. We learned that IgA-EBA is clinically indistinguishable from the classic "lamina-lucida type" linear IgA dermatosis or from the inflammatory type of IgG-mediated epidermolysis bullosa acquisita (IgG-EBA). Only a minority of the patients with IgA-EBA showed milia or scarring or had therapy-resistant ocular symptoms as in the mechanobullous type of IgG-EBA. Most patients with IgA-EBA responded to dapsone therapy.