It is widely regarded that the HLA class II alleles HLA-DRB1*04:02 and HLA-DQB1*05:03 confer susceptibility to PV (10) and Dsg3-reactive CD4+ T cell responses against the ectodomain of Dsg3 were identified in PV patients (11). The gene discussed is HLA-DRB1; the disease is acquired polycythemia vera.