Cutaneous pemphigus vulgaris with absence of desmoglein 1 autoantibodies. An example of the extended desmoglein compensation theory.

A 79 year-old male patient presented clinically as a typical case of pemphigus foliaceus. He displayed a seborrhoeic pattern of crusting and erosions with an absence of oral involvement. Surprisingly, a biopsy showed suprabasilar acantholysis and direct immunofluorescence consistent with pemphigus vulgaris. Indirect pemphigus antibodies were positive for desmoglein 3 (DSG-3) but negative for DSG-1 antibodies. Most cases of cutaneous pemphigus are reported to have both DSG-1 and DSG-3 antibodies. A rare cutaneous subtype of pemphigus vulgaris is reported in the literature that may present clinically as seen in our patient. Our patient is clinically similar to these previous reported cases but with a negative DSG-1 antibody titre. The extended DSG compensation theory explains the differences of clinical expression in pemphigus based on the variable pathogenicity of DSG antibodies as well as the distribution of DSG-1 and DSG-3. We discuss this case, highlighting the theories of the pathogenesis of pemphigus and, in particular, the cutaneous pemphigus subtype.