Abnormal proliferation of plasma cells and some monoclonal B cells frequently cause the secretion of monoclonal immunoglobulins or immunoglobulin fragments into the serum, causing monoclonal gammopathy, which leads to various diseases including renal diseases. Therefore, monoclonal gammopathy is frequently associated with kidney diseases, including glomerular and tubulointerstitial diseases. Glomerular disease, with the deposition of monoclonal immunoglobulins or their components, includes monoclonal immunoglobulin deposition disease (MIDD), AL or AH amyloidosis, type I cryoglobulinemia, proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID), immunotactoid glomerulopathy, and fibrillary glomerulonephritis. In addition, tubulointerstitial diseases with the deposition of monoclonal immunoglobulins or their components are constituted by light chain (myeloma) cast nephropathy, light chain associated Fanconi's syndrome (light chain proximal [crystal] tubulopathy), and crystal-storing histiocytosis. In the present review article, we demonstrate the clinicopathological characteristics of MIDD, which is one of the representative diseases of plasma cell dyscrasias, and discuss various renal diseases with the deposition of monoclonal immunoglobulins or their components in glomeruli and the tubulointerstitium. We recommend that these renal diseases are arranged as one disease category, "renal diseases with deposition of monoclonal immunoglobulins or their components", in order to simplify the understanding of complicated diseases in plasma cell dysplasia.
Keywords: glomerular deposition disease; light chain deposition disease (LCDD); monoclonal gammopathy of renal significance (MGRS); monoclonal gammopathy of undetermined significance (MGUS); monoclonal immunoglobulin deposition disease (MIDD).