Kidney Injury in Multiple Myeloma: A Kidney Biopsy Teaching Case

Abstract Myeloma-related kidney disease has several manifestations; the two most common histological diagnoses are myeloma cast nephropathy and acute tubular necrosis. We describe a case of different kidney pathologies occurring concomitantly in a patient found to have IgA kappa multiple myeloma.A white woman in her 70s presented with 8 months history of back pain and was found to have nephrotic range proteinuria and acute kidney injury. Her serum calcium was 12.6 mg/dL. Kidney biopsy showed kappa light chain only proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID), crystalglobulinemia, light chain proximal tubulopathy with kappa light chain deposits, mild tubular atrophy and interstitial fibrosis. Free kappa light chain ratio was >1000 mg/dL and free kappa light chain level was 4670 mg /dL. Within a week following treatment of hypercalcemia and initiation of chemotherapy, her acute kidney injury and hypercalcemia resolved. This case highlights the many kidney manifestations of multiple myeloma and that prompt management targeting these manifestations including hypercalcemia can improve clinical outcomes