Abstract: FR-PO1287
When Proteinuria Doesn't Match Albumin: A Clue to Atypical Multiple Myeloma
Session Information
- Onconephrology: Diagnostic Dilemmas, Therapy-Related Toxicities, and Clinical Cases
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Onconephrology
- 1600 Onconephrology
Authors
- Abalos, Cherylene S., Banner - University Medical Center Tucson, Tucson, Arizona, United States
- Murugapandian, Sangeetha, Banner - University Medical Center Tucson, Tucson, Arizona, United States
- Vahdani, Golnaz, Banner - University Medical Center Tucson, Tucson, Arizona, United States
Introduction
Multiple myeloma (MM) classically presents with “CRAB” features (hypercalcemia, renal impairment, anemia and lytic bone disease). Renal screening often begins with urinalysis for proteinuria evaluation, followed by monoclonal workup (SPEP, UPEP, immunofixation, serum free light chains) when indicated. We describe an atypical presentation manifesting as recurrent chylous pleural effusions and progressive lymphedema, where a significant UACR-UPCR gap- rather than overt renal failure, prompted life saving diagnosis.
Case Description
A 71-year-old man with hypertension presented with worsening anasarca and recurrent pleural effusions, requiring pleurodesis and PleurX catheters. Pleural fluid studies and biopsies were non-diagnostic. He re-presented with progressive edema and hypoxemia. CT demonstrated pulmonary emboli and extensive sheetlike soft-tissue hyper densities in the retroperitoneum and mediastinum. Renal function was preserved (Cr 0.7 mg/dL). Initial labs showed a Hemoglobin of 11.3 g/dL, corrected Ca 9.7 mg/dL, total protein 4.7 g/dL, A/G ratio 0.9. Urinalysis showed moderate protein; urine ACR 44 mg/g, urine protein-creatinine ratio 578 mg/g. Nephrology was consulted for proteinuria. Given concern for non-albumin proteinuria monoclonal evaluation was pursued. Serum free light chains revealed a kappa predominance (kappa/lambda ratio 32.65; kappa FLC 685 mg/L). SPEP, UPEP, and immunofixation were positive. Bone marrow biopsy demonstrated 30–40% clonal kappa plasma cells, confirming multiple myeloma.
Discussion
This case highlights the diagnostic value of UACR–UPCR discordance, suggesting non-albumin (light chain) proteinuria. In multiple myeloma, excess free light chains exceed proximal tubular reabsorptive capacity, causing overflow (non-albumin) proteinuria that may be missed by albumin-based screening. Chylothorax and lymphedema are rare myeloma manifestations (≈1–4%), often signifying extramedullary disease that may reflect thoracic duct compression, direct pleural infiltration, or lymphatic obstruction by tumor. This case underscores the need for a high index of suspicion and a comprehensive monoclonal workup in older patients with unexplained proteinuria and systemic findings, particularly when there is a UACR- UPCR gap, even when renal function is preserved and classic myeloma features are absent.