Immunogenetic studies show an important association between susceptibility to PV and HLA-DRB1*04:02, primarily in Ashkenazi Jews, and HLA-DRB1*14:01, HLA-DRB1*14:04, and HLA-DQB1*05:03, prevalent in non-Jewish patients of European and Asian descent [24]. The gene discussed is HLA-DRB1; the disease is acquired polycythemia vera.