Pemphigus vulgaris (PV) is a chronic, potentially lethal autoimmune mucocutaneous bullous disease mediated by essentially IgG autoantibodies directed against desmogleins 1 and 3 (Dsg1 and Dsg3), cadherin-type cell–cell adhesion molecules present in desmosomes [1]. The gene discussed is DSG1; the disease is acquired polycythemia vera.