Long term outcomes in monoclonal gammopathy of renal significance.

Unlike AL amyloid and cast nephropathy, the long-term outcomes of monoclonal gammopathy of renal significance (MGRS) patients with other renal histopathologies remain unclear. It is uncertain if early intervention improves renal outcomes, because of a lack of evidence from prospective studies. In this retrospective study, we examined outcomes of 41 MGRS patients treated between 2004 and 2017 across five centres: four in the UK and one in the Republic of Ireland. The primary outcome measure was renal survival estimated by Kaplan-Meier product-limit method. Thirty-three patients (80·5%) were kappa light chain (LC) restricted. Twenty-seven patients (65·9%) presented with LC deposition disease on renal histology. At 24 months follow-up, estimated renal survival was 81·6% for the whole cohort. The estimated overall survival was 80·3% at 48 months. At 24 months, patients who had chronic kidney disease (CKD) stage 2-3b at diagnosis showed an estimated renal survival of 100% compared to 80·7% in those with CKD stage 4-5 at diagnosis (P = 0·04). Poorer outcomes in MGRS patients were historically attributed to delayed diagnosis due to small plasma cell clones, as well as the need for renal biopsy.