Mesangial proliferative glomerulonephritis with monoclonal immunoglobulin deposits: why nephrobiopsy is crucial

Proliferative glomerulonephritis (GN) with monoclonal immunoglobulin deposits (PGNMIDs) is a recently described entity among the spectrum of monoclonal gammopathy of renal significance (MGRS). The disease is renal limited and manifests in chronic glomerular disease, altered renal function and albumi­nuria, sometimes in the nephrotic range. Acute nephritic syndrome is rare. Until recently, in the absence of criteria for symptomatic haematological disease, patients with monoclonal Ig-related nephropathies often experienced difficulties in getting appropriate chemotherapy. Noticeable progress in management was achieved with the introduction of the concept of monoclonal gammopathy of renal significance, which distinguishes the situation of nephropathies induced by dangerous small B-cell clones from that of monoclonal gammopathy of undetermined significance (MGUS) that does not feature any end-organ damage. Monoclonal gammapathy of renal significance is not an independent kidney disease, not “chronic glomerulonephritis”, but a condition in which kidney damage is secondary to clonal B-cell proliferation. In other words, MGRS is a precancerous disease combined with chronic kidney disease that requires immediate treatment. Renal prognosis is poor, with progression to end stage renal disease in 25 % of patients wi­thin 30 months and frequent early recurrence on the renal allograft. However, recent studies indicate that clone-targeted chemotherapy may significantly improve renal outcomes, opening future perspectives for the management of this rare disease.