William J. Placzek et al. evaluated the association between serum Gd-IgA1 levels and IgG or IgA serum Gd-IgA1-specific autoantibodies from 135 adult patients with histopathologically confirmed IgA nephropathy, 76 patients with other renal diseases and 106 healthy individuals [22]. Here, IGHA1 is linked to IgA glomerulonephritis.