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Kidney Week

Abstract: SA-PO939

Kappa-Restricted Light Chain Proximal Tubulopathy (LCPT) in Waldenström Macroglobulinemia (WM)

Session Information

Category: CKD (Non-Dialysis)

  • 2202 CKD (Non-Dialysis): Clinical‚ Outcomes‚ and Trials

Authors

  • Zhang, Yani, MedStar Union Memorial Hospital, Baltimore, Maryland, United States
  • Kwon, Donghyang, MedStar Georgetown University Hospital, Washington, District of Columbia, United States
  • Choi, Michael J., MedStar Georgetown University Hospital, Washington, District of Columbia, United States
Introduction

WM is a lymphoproliferative disorder with possible renal involvement from high tumor burden of IgM monoclonal protein or monoclonal gammopathy of renal significance (low tumor burden). LCPT is a rare cause for progressive kidney dysfunction in WM.

Case Description

A 62-yo man with CKD 3a from unknown cause and WM diagnosed 2 years ago presented with a serum creatinine of 1.71 mg/dL (1.38 mg/dL 15 months prior). Work up revealed serum albumin 4.8 g/dL, IgM 4,596 mg/dl, free K:L ratio 31, M-spike: 2.5 mg/dL, uric acid 1.7 mg/dL, phosphorus 3.3 mg/dL, LDH 153 u/L, viscosity 2.8, C3 81 mg/dL, UA: 1+ protein, trace glucose (serum glucose 87 mg/dl), pH 7, 0 RBCs or WBCs/HPF. 24-hr urine protein 2,139 mg, urine protein electrophoresis showed albumin 22.6%, and M spike 26.6%. Renal ultrasound unremarkable. Kidney biopsy revealed k-LCPT [Figure].
Serum parameters improved with stable proteinuria after therapy for WM with bortezomib, rituximab and dexamethasone.

Discussion

Crystalline k-LCPT is a rare renal presentation of WM in which monoclonal light chain can accumulate in proximal tubular cells when light chain production exceeds proximal tubule reabsorption capacity and lysosomal degradation. Clinicians should consider this disease in WM patients with CKD, sub-nephrotic proteinuria, and evidence of proximal tubulopathy with or without complete Fanconi syndrome.

Proximal tubules show eosinophilic amorphous granular material in the cytoplasm and lumen.

PTC shows intracytoplasmic and membrane-bound crystalline structures with rhomboid shapes.