DSG1 and acquired polycythemia vera: Pemphigus vulgaris (PV), a rare, potentially fatal autoimmune disorder characterized by the production of autoantibodies against desmosomal proteins, particularly desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1), serves as a classic example of an organ-specific autoimmune disease where significant genetic predisposition is well established.