Given that PV1-IgG contained more than 200 U/ml of anti-Dsg3-antibodies but only 59 U/ml of anti-Dsg1 autoantibodies, and PV2-IgG and PV3-IgG were from patient with mucosal PV, we repeated the dissociation assay with a PV-IgG from another mucocutaneous PV patient (designated PV4-IgG). This evidence concerns the gene DSG1 and acquired polycythemia vera.