Clinical Presentation and Renal Histopathological Findings in Patients with Monoclonal Gammopathy and Kidney Disease

Monoclonal gammopathies have been associated with kidney injury. Nephrotoxicity of the secreted monoclonal (M)-protein relies on a complex interplay between biological characteristics and serum concentration. Little is known about the epidemiology and clinical manifestations of the different types of monoclonal gammopathies in patients with kidney disease. We enrolled all patients with monoclonal gammopathy who underwent kidney biopsy between January 2000 and March 2017. Data about demographics, clinical manifestations and histological lesions were collected retrospectively. Monoclonal gammopathy was detected in 174 (13%) patients with a mean age of 66.4{+/-}13.1 years. M-protein was secreted by monoclonal gammopathy of undetermined significate (MGUS) (52,8%), myeloma multiple (MM) (25.2%), primary amyloidosis (AL) (9,1%), smoldering MM (7 %), non-Hodgkin lymphoma (NHL) (6.8%) and HL (1.7%). Monoclonal gammopathy of renal significance (MGRS) accounted for 6.5% in patients with MGUS and 14.2% in patients with smoldering MM. Evaluation of kidney biopsy revealed that M-protein was directed involved in causing kidney injury in MM (93.1%) and NHL (8,3%). MM was the only gammopathy significantly associated with an increased risk of kidney injury (odds ratio [OR]=47.5, CI95%, 13.7-164.9; P=<0.001). While there were no significant differences in the progression toward end-stage renal disease or dialysis (P=0.776), these disorders were associated with a different risk of death (P=0.047) at the end of the follow-up. Monoclonal gammopathy was a frequent finding in patients with kidney disease. Kidney biopsy had a key role in identifying the underlying monoclonal gammopathy and recognizing the causal relationship between M-protein and kidney injury.