PV more commonly presents in individuals with genetic predisposing factors including the human leukocyte antigen (HLA)-DR4 and HLA-DR6 serotypes.13 Several trigger factors for PV have been identified including phenol and thiol drugs, infection, trauma, and stress.14 The activation of B-cells producing anti-Dsg1/3 autoantibodies is promoted by interactions with Th2 cells through the action of cytokines including IL-4, which also promotes isotype switching from IgG1 to IgG4.15 Isotypes of anti-Dsg3 autoantibodies identified in this study were primarily IgG1 and IgG4 (Supplemental Table 6). Here, DSG1 is linked to acquired polycythemia vera.