Pemphigus vulgaris (PV) is the most common subtype of a group of rare autoimmune blistering disorders (AIBD) in which autoantibodies primarily directed against the cell-cell adhesion molecules desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1) lead to characteristic epidermal blistering. This evidence concerns the gene DSG1 and acquired polycythemia vera.