HLA-DRB1 and nephritis: In order to determine the possible influence of the HLA-DRB1 polymorphism on different clinical manifestations of IgAV, the patient group was also divided into four subgroups: patients with GI involvement (IgAV and GI, N = 31), patients with nephritis (IgAVN, N = 20), patients with both GI involvement and nephritis (IgAVN and GI, N = 19) and patients without GI involvement and nephritis (IgAV, N = 60).