HSPG2 and acquired polycythemia vera: Because antibodies against Dsg1 are known to be important for epidermal blistering and Dsg1 was reported to regulate signalling mechanisms in part differently compared to Dsg3 such as activation of the PLC/Ca2+ pathway, the prevalence of extradesmosmal Dsg1 at sites of blister formation in PV and PF would explain differences in the clinical phenotypes of pemphigus.