An update on paraprotein-related renal pathology

Abstract

Paraproteins are intact monoclonal immunoglobulins (MIg) or isolated MIg heavy or light chains, detected in the blood or urine and caused by a clonal proliferation of B cells or plasma cells. Paraproteins often cause renal injury, referred to here as paraprotein-related renal disease (PPRD), whether the underlying clonal disorder is characterized by high tumour burden requiring treatment or low tumour burden and thus not requiring immediate treatment from the haematological standpoint. For the latter, an important recent update is the introduction of the concept of Monoclonal Gammopathy of Renal Significance (MGRS), in which the renal pathology in itself may justify the use of clone-directed therapies targeting the nephrotoxic clone, in order to preserve renal function. A bewildering array of renal pathology can be caused by paraproteins, affecting all compartments of the kidney – glomeruli, tubules, interstitium and blood vessels. This review aims to provide an overview of the different renal lesions that can be seen, organized by predominant compartment affected, with guidance on how to spot them and classify them.