Pre Transplantation MGUS and Transformation to Multiple Myeloma in Kidney Transplantation: A Single Center Experience.

Abstract Background: Monoclonal gammopathy of undetermined significance (MGUS) is reported in 3 to 5 percent of population, with the prevalence increasing with advancing age. Patients with MGUS are at increased risk for progression to multiple myeloma or other plasma cell dyscrasias. There is a paucity of information on clinical outcomes of patients with MGUS undergoing renal transplantation. A retrospective study was performed to determine wether MGUS is a contraindication to renal transplantation. Methods: Data was collected from both the kidney transplant and MGUS database. The diagnosis of MGUS was made on the basis of either serum protein electrophoresis (SPEP) or immunofixation after excluding multiple myeloma, amyloidosis and monoclonal immunoglobulin deposition disease. Results: Between 1977 and 2004, 3518 patients underwent kidney transplantation of whom 23 patients had a preexisting monoclonal gammopathy of undetermined significance (MGUS). Fourteen (61%) of these patients were males. The median age at the time of transplant was 59 ±12 years. Ten patients (43.5%) had IgG Kappa (GK), 7 (30.4%) had IgG Lambda (GL), 2 (8.7%) had IgA Lambda (AL), 1 (4.3%) had IgA Kappa (AK), 2 (8.7%) had IgM Lambda (ML). One patient had a biclonal gammopathy GL and ML. Patients were monitored with either SPEP or immunofixation for median duration of 1542 days after transplantation. Thirteen patients had either no change or stable monoclonal protein, 6 had a decrease in their paraprotein level. Two patients had a mild increase in their paraprotein. Two patients with GK developed into biclonal gammopathy (GK and AK). The median follow up of this cohort after the renal transplant was 1783 days. Twelve (52%) patients remained alive at the time of the study. A patient with GK prior to the transplant who underwent kidney transplantation twice developed a biclonal gammopathy and was found to have increased plasma cells (20%) in bone marrow after 14 years. On follow up for 6 years, his M-protein remained stable. Another patient was found to have 17% plasma cells around the time of kidney transplantation. He had a stable M-protein at follow-up, but underwent a stem cell transplant for recurrent immunotactoid glomerulonephritis. Two (9%) patients developed more than 15% plasma cells in their bone marrow with a stable M-protein. None of the patients with a preexisting MGUS evolved into multiple myeloma. Conclusion: In this small study, the presence of MGUS prior to kidney transplantation did not appear to have increased the incidence of multiple myeloma post transplant. Therefore, MGUS by itself should not be considered as an absolute contraindication for renal transplantation.