2024-11-1020220041-1337N/Ahttps://hdl.handle.net/20.500.14288/16644Introduction: Monoclonal gammopathy of renal significance (MGRS) is a recently defined group of renal diseases caused by monoclonal immunoglobulin secreted by nonmalignant proliferative B cell or plasma cell causes renal damage. Here we report a case known as primary kidney disease C3 glomerulonephritis but after kidney transplant diagnosed MGRS. Case presentation: A 32-year old man underwent live related renal transplant in December 2020 for ESRF secondary C3 glomerulonephritis. At 2 months post-transplant, his serum kreatinin levels increased from a basaline creatinine of 1.2 mg/dl to 1.7mg/dl, and he developed proteinuria (1.2 gr/day). Renal biopsy showed monoclonal membranoproliferative glomerulonephritis. His serum and urine kappa/lambda light chain ratio was normal and he had no monoclonal protein in serum and urine immunfixation electrophoresis. After the patient was treated with Rituximab (4 cycles), his serum creatinin levels and proteinuria increased and repeat biopsy showed increase of monoclonal immun complexes in glomeruler capillers. The patient was treated bortezomib-based chemotherapy (4 cycles). Repeat biopsy showed no regression renal pathology. His renal functions and proteinuria continued to deteriorate. There were a rise in urine kappa/lambda light chain ratio. He received no further chemotherapy, a decision was taken to manage her kidney condition conservatively. Conclusions: Monoclonol immunoglobulin deposits may not be detectable in standart immunofluorescence techniques and can result missing the diagnosis of MGRS. Patiens with C3glomerulonephritis should be examined in detail for monoclonal gammapathy before kidney transplantation. ImmunologySurgeryTransplantation immunologyMeeting Abstract1534-6080889117001269Q19352