Patients with monoclonal gammopathy and concurrent renal illness are common in clinical practice. Because of the existence of monoclonal Ig–related kidney damage, some of them were diagnosed with monoclonal gammopathy of renal significance (MGRS). For a study, researchers sought to examine the histopathologic spectrum and clinical aspects associated with MGRS in a large cohort of patients from a single nephrology referral hospital who had monoclonal gammopathy and biopsy-proven kidney disorders.

The retrospective analysis included patients who reported monoclonal gammopathy (monoclonal spike on serum and/or urine immunofixation tests) and underwent kidney biopsy at Hospital between January 1, 1999, and December 31, 2020. Patients with malignant hematologic disorders were barred from participating. The electronic medical record system was used to gather clinical and laboratory data. There were comparisons between patients with and without MGRS, as well as between patients with and without amyloidosis. Using multivariable logistic regression, the clinical features linked with MGRS were discovered.

A total of 700 patients were identified as having monoclonal gammopathy and a kidney biopsy. About 13 patients who had repeat kidney biopsies were studied individually. The remaining 687 patients with 1 kidney biopsy had MGRS lesions in 261 (38%) and non-MGRS kidney disorders in the remaining 426 (62%) patients. The majority MGRS patients (n=164, 63%) were caused by Ig-related amyloidosis, followed by monoclonal Ig deposition disease (n=23, 9%) and thrombotic microangiopathy (n=22, 8%). The most prevalent diagnosis in the non-MGRS group (n=171, 40 percent) was membranous nephropathy. The existence of an aberrant serum free light chain ratio, being older, and having more proteinuria were all independently linked with MGRS in the multivariable logistic regression model.

In patients with monoclonal gammopathy, monoclonal Ig amyloidosis was the most common cause of MGRS. MGRS was linked to an irregular free light chain ratio, being older, and having more proteinuria.