IgA pemphigus - Occurrence of anti-Desmocollin 1 and anti-desmoglein 1 antibody reactivity in an individual patient

Background: IgA pemphigus is a rare pustular autoimmune disease with exclusive IgA anti-keratinocyte cell surface antibody reactivity. Two subtypes have been discerned: in the subcorneal pustular dermatosis type, desmocollin 1 has been identified as a targeted autoantigen, while in few cases of the intraepidermal neutrophilic type, IgA anti-desmoglein 1 or IgA anti-desmoglein 3 reactivity has been demonstrated. Patients and Methods: A 48-year-old white male presented with generalized large confluent pustules. Skin pathology was assessed by histology and direct immunofluorescence analysis. IgG/IgA autoantibodies against desmoglein 1/3 and desmocollin 1 were measured by ELISA and indirect immunofluorescence using desmocollin 1 cDNA-transfected COS7 cells, respectively. Results: Histopathology revealed subcorneal pustules and direct immunofluorescence microscopy exclusively showed in vivo bound IgA with an intercellular pattern in the epidermis. Desmocollin 1 was identified as a target of IgA autoantibodies by indirect immunofluorescence microscopy utilizing desmocollin 1 cDNA-transfected COS7 cells. In addition, IgA anti-desmoglein 1 reactivity was demonstrated by ELISA. Neither IgA anti-desmoglein 3 nor IgG anti-desmoglein 1/3 autoantibodies were present. Conclusions: Both desmocollin 1 and desmoglein 1 were autoantigens in this patient with IgA pemphigus and a distinct clinical presentation. To our knowledge, this is the first IgA pemphigus case with dual autoantibody reactivity.