Renal lesions associated with monoclonal gammopathies of undetermined significance: clinical forms, mechanisms of development, approaches to treatment

Abstract

The term «monoclonal gammopathies of undetermined significance» (MGUS) was introduced by R. Kyle in 1978 to designate the condition characterized by the presence ofsmall amounts ofM-protein in the serum. In some patients, such condition remains benign for a long time but predetermines for the development of multiple myeloma and other B-lymphocytic tumours. Also, it can provoke non-cancerous diseases due to the toxic action of monoclonal proteins (immunoglobulins and free light chains) on various organs, especially kidneys. MGUS-associated renal lesions include glomerulopathies with organized deposits, such as AL-amyloidosis (amyloid light chain of immunoglobulin), cryoglobulinic and immunotactoid glomerulonephritis, and with unorganized deposits (light chain deposition and proliferative forms of idiopathic glomerulonephritis. The available experimental data throw light on the possible mechanisms of renal lesions. We summarized the literature data and original observations to describe methods for differential diagnostics of MGUS-associated renal lesions including the highly sensitive test for free light chine identification (Freelite method) and principles of pathogenetic treatment by the impact on the pathological B-cell clone.