Transition from pemphigus foliaceus to bullous pemphigoid: intermolecular B-cell epitope spreading without IgG subclass shifting.

Pemphigus and the pemphigoid group of diseases are distinct autoimmune conditions in which autoantibodies with different specificities cause skin blistering by different mechanisms. Transitions and associations between these two groups of autoimmune diseases are rare. Here, we report a patient with long-standing pemphigus foliaceus, in whom clinical remission was eventually induced. Shortly thereafter, he developed the clinical, histologic, and immunopathological changes of bullous pemphigoid. This case offered the rare opportunity to serologically monitor serum levels of both anti-BP180 and BP230 during the preclinical stage of bullous pemphigoid. Of interest, although the autoimmune response clearly shifted with regard to the target antigens, the patient's autoantibodies against desmosomal and hemidesmosomal components showed the same IgG subclass distribution.