Paraproteinemia and renal involvement

Renal manifestations in patients with monoclonal paraproteinemia are frequent. Cast nephropathy is a disease that only occurs in manifest multiple myeloma with a high tumor burden. In contrast, monoclonal gammopathy of renal significance (MGRS) is defined as renal involvement due to a nephrotoxic clone that from a hematological standpoint would per se not require treatment. The diagnosis of MGRS can only be made by renal biopsy. Here monotypic immunoglobulin (Ig) deposits can be found in either organized (amyloidosis, fibrillary glomerulonephritis, GN, immunotactoid GN, cryoglobulinemic GN) or nonorganized forms (monoclonal Ig deposition disease, proliferative GN with monoclonal Ig deposits). There are two forms of MGRS that can occur without the deposition of Ig, namely C3 glomerulopathy and thrombotic microangiopathy. For cast nephropathy there is always a fundamental indication for chemotherapy. The data on mechanical elimination of light chains by plasmapheresis or high cut-off dialysis are inconsistent. In patients with MGRS the indications for treatment must be made based on the renal prognosis in a cooperation between nephrologists and hematologists. Only a clone-directed treatment can lead to an improvement of renal function.