According to these studies, patients with IgAN have aberrant IgA1 molecules with a Gal deficiency of O-linked glycans in the hinge region, which indicates that Gd-IgA1 consists of terminal N-acetyl-galactosamine (GalNAc) or sialylated GalNAc [20–23]. This evidence concerns the gene IGHA1 and hyperinsulinemic hypoglycemia, familial, 4.