Abstract: A 56yearold woman presented with oliguric acute renal failure,rib fracture and anemia.Serum immunofixation electrophoresis identified a monoclonal immunoglobulin (Ig) G and λ protein.The free κ/λ ratio was abnormal and urine BenceJones protein was positive.Bone marrow biopsy revealed plasmocytosis (17%).A kidney biopsy was performed and showed light chain cast nephropathy with crystal formation.Finally,the patient was diagnosed with multiple myeloma (DSS ⅢB),crystalline light chain cast nephropathy and acute kidney injury stage 3.