Increased production of IgA1 in the bone marrow is thought to be responsible for the elevation of serum IgA1 [19, 20]; however, IgA-producing myeloma is usually unaccompanied by IgAN, and only the patients with aberrantly glycosylated IgA1 develop glomerulonephritis in cases with IgA1 multiple myeloma [21, 22]. The gene discussed is IGHA1; the disease is glomerulonephritis.