HLA-DRB1 and acquired polycythemia vera: HLA-DRB1*04:02, HLA-DRB1*14 (14:01, 14:05, and 14:06), and HLA-DQB1*05:03 alleles are associated with PV, and HLA-DRB1*04 and HLA-DRB1*14 alleles are associated with PF and HLA-DRB1*01 alleles are especially associated with an endemic form of PF, also known as fogo selvagem (3, 14, 15).