HLA-DRB1 and acquired polycythemia vera: For specific purposes, the following were evaluated: (i) Demographic and clinical data; (ii) Temporal evolution of anti-Dsg1 and 3 titers by ELISA and identification of Dsg1 and 3 by immunoblotting (IB) in the PF-anti-Dsg3+ group; and (iii) Expression of Dsg1 and 3 in paraffin-embedded skin biopsies by immunohistochemistry (IHC) and (iv) typification of HLA-DRB1 alleles associated with PF and PV in the PF-anti-Dsg3+ and PF-anti-Dsg3(-) groups.