Subcorneal Pustular Dermatosis-Type IgA Pemphigus With Autoantibodies to Desmocollins 1, 2, and 3

Background IgA pemphigus is a rare neutrophilic acantholytic autoimmune disease that is characterized by IgA deposits on keratinocyte cell surfaces. Clinically and histologically, IgA pemphigus is divided into 2 major subtypes: subcorneal pustular dermatosis and intraepidermal neutrophilic IgA dermatosis. We report the first case of subcorneal pustular dermatosis–type IgA pemphigus that showed reactivity to all 3 isoforms of the desmocollin family by indirect immunofluorescence microscopy of COS7 cells transfected with desmocollin 1, 2, or 3. Observations We describe a 94-year-old woman with IgA pemphigus with a unique immunopathologic pattern. Direct immunofluorescence microscopy revealed IgA deposits throughout the entire epidermis, with stronger staining in the upper epidermis. The autoantibodies from this patient did not show IgA or IgG reactivity with desmogleins via immunoblotting or enzyme-linked immunosorbent assay. By indirect immunofluorescence by the use of COS7 cells transfected with desmocollin 1, 2, or 3, IgA autoantibodies in a serum sample from our patient clearly reacted with all of them. Conclusions The pathophysiology and autoantigen profile of bullous autoimmune diseases, especially pemphigus and its subforms, are more complex than previously believed. Because pemphigus seems to be a heterogeneous disorder, further studies are needed to evaluate the complexity of the disease.