Nephrotic syndrome secondary to amyloidosis in a patient with monoclonal gammopathy with renal significance (MGRS).

Monoclonal gammopathy with renal significance (MGRS) is a relative new-described entity, diagnosed especially in older patients and deriving from the group with monoclonal gammopathy of undetermined significance (MGUS). Various renal lesions may arise in MGRS, according to the ultrastructural characteristics of the monoclonal immunoglobulin deposition in the kidney, from proliferative glomerulopathies and amyloidosis to light chain proximal tubulopathy and crystal-storing histiocytosis. Although both are considered premalign or non-malignant hematological conditions, kidney involvement in MGRS aggravates the prognosis of the patients and need to be treated aggressively. We discuss the case of a 44-year-old female patient admitted in our Department of Nephrology for clinical picture of impure nephrotic syndrome and decreased renal function associated with Bence-Jones proteinuria. Renal biopsy was performed, and fibrillar amyloid deposits were demonstrated both in glomerular and tubular basement membranes; the immunofluorescence identified the presence of κ chains. Bone marrow aspiration and biopsy showed <10% plasmocytic proliferation confirming the diagnosis of MGRS.