Cyclophosphamide for the Treatment of Proliferative Glomerulonephritis with Monoclonal Immunoglobulin Deposition.

About 3% of the population aged more than 50 years, is affected by monoclonal gammopathy of undetermined significance (MGUS), a premalignant condition that may progress to lymphoproliferative disorders. Since MGUS does not represent the diseases associated with end organ damage, a new term, monoclonal gammopathy of renal significance (MGRS) is coined for the monoclonal gammopathies that are associated with renal disorders. MGRS is classified into various types, including monoclonal immunoglobulin deposition disease (MIDD) and proliferative glomerulonephritis with monoclonal immunoglobulin deposition (PGNMID). PGNMID presents with membranoproliferative glomerulonephritis-type lesions associated with immunoglobulin deposition. This disease entity has a poor prognosis and its optimum treatment is yet to be established. We present the case of an elderly male, a known patient of light chain deposition disease, a form of MIDD, who initially lost to follow-up but later presented with PGNMID, wherein he was treated with steroid and cyclophosphamide, to which he responded.