Real-World Outcomes of Patients with Monoclonal Gammopathy of Renal Significance

Background: Monoclonal gammopathy of renal significance (MGRS) is a rare group of renal disorders caused by monoclonal immunoglobulins from non-malignant B-cell or plasma cell clones, with distinct amyloid (MGRS-A) and non-amyloid (MGRS-NA) subtypes. Although these are often grouped together, whether they share similar clinical phenotypes and outcomes is uncertain. We therefore examined similarities and differences between these subtypes in a contemporary real-world cohort.

We performed a single-centre retrospective evaluation of 17 biopsy-confirmed MGRS patients (10 MGRS-A, 7 MGRS-NA). Baseline parameters, treatment exposure, renal and haematologic responses, survival, and relapse were analysed descriptively with exploratory subgroup comparisons.

MGRS-NA patients presented with significantly worse baseline renal function (median estimated glomerular filtration rate 18.0 mL/min/1.73 m2 vs. 49.0 mL/min/1.73 m2 in MGRS-A, p < 0.05) and progressed faster to dialysis (p < 0.01). Haematologic responses (≥VGPR) were achieved in 57.1% of MGRS-NA and 50% of MGRS-A patients, but these did not significantly correlate with renal improvement. Survival was similar between groups, with deaths in 28.6% of MGRS-NA and 20% of MGRS-A. Relapse occurred in 47.1% of patients, with median times of 51 months in MGRS-NA and 69 months in MGRS-A. Treatment, primarily bortezomib-based chemotherapy, was associated with toxicities (94.1%), yet renal responses remained limited.

The findings highlight the poor prognosis and rapid renal decline in MGRS-NA. We highlight the need for early diagnosis and an integrated renal-haematologic service to improve outcomes in this rare population.