[Renal involvement in benign monoclonal gammopathies: an underdiagnosed condition]

Renal involvement is observed frequently in association with malignant gammopathies, mainly those related to light chain deposition, although has also been described in non-malignant monoclonal gammopathy. This study reports the clinicopathological findings and outcome in 9 patients with nephropaty secondary to monoclonal immunoglobulin deposit in absence of malignancy. They were three men and six women and they were 59.2+/-12 years old. All patients presented proteinuria and different levels of renal insufficiency (mean creatinin = 315+/-187 micromol/L) at the moment of diagnostic. Two patients required dialysis at the time of renal biopsy. The pathology studies revealed a nodular sclerosing glomerulopathy in four cases, mesangiocapilary glomerulonephritis in three cases, only tubular lesions in one and mesangial lesions in the other one. The treatment applied was: Prednisone alone (two cases), with chemotherapy associated (melfalan in two, clorambucil in one and ciclophosphamide in another one). One patient received plasmapheresis and mycophenolate and another patient undergone a bone marrow authotransplant associated to mycophenolate and prednisone. One of the two patients who required dialysis at the moment of presentation was not treated. After a follow-up of more than 4 years (4.89 +/-DE: 3.69) renal function improved or remained stable in three patients and proteinuria was disappeared in more than 50% of patients. Four patients had a worsening of renal function and they required dialysis during the time of follow-up (in 2,4 years +/- DE: 4,3). In any case malignitation was observed. Chemotherapy stabilized or improved renal function in 3 of nine patients (33%) with non-malignant monoclonal gammopathy. Non-malignant monoclonal gammopathy could go unnoticed. Appearance of abnormalities in renal routine tests deserves more in-depth diagnostic procedures, including renal biopsy. Evolution to end stage renal disease could probably be avoided or reduced in severity with early detection and treatment of this entity.