found that 41% of Japanese IgAN patients had serum levels of Gd-IgA1 above the 90th percentile of normal, and 91% had anti-Gd-IgA1 IgG antibodies above the 90th percentile of normal, as did up to 25% of patients with other kidney diseases, especially immune-mediated diseases such as lupus nephritis (27). This evidence concerns the gene IGHA1 and kidney disorder.