Finally, to assess the potential relationship between C5 and C5AR1 and demographic and clinical characteristics of IgAV other than nephritis and sex, C5 and C5AR1 genetic frequencies were compared amongst IgAV patients stratified according to the age at the disease onset, the presence/absence of joint and GI damage, and according to whether IgAV patients were female or male. This evidence concerns the gene C5AR1 and nephritis.