HLA-DRB1 and acquired polycythemia vera: Studies have shown that HLA alleles DRB1*04:02 and DQB1*05:03 represent the most common PV associated alleles (Ahmed et al., 1991; Carcassi et al., 1996; Delgado et al., 1996; Lee et al., 1998; Lombardi et al., 1999; Loiseau et al., 2000; Miyagawa et al., 2002; Geng et al., 2005; Liu et al., 2008; Shams et al., 2009; Tunca et al., 2010; Párnická et al., 2013; Brochado et al., 2016), with the majority of the patients with PV expressing one of these two alleles.