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Kidney Week

Abstract: PO2198

Masked Light Chain Proximal Tubulopathy (LCPT) and Focal Segmental Glomerulosclerosis (FSGS) in Multiple Myeloma (MM)

Session Information

  • Onco-Nephrology - 2
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: Trainee Case Report

  • 1500 Onco-Nephrology

Authors

  • Abramson, Matthew, Memorial Sloan Kettering Cancer Center, New York, New York, United States
  • Seshan, Surya V., Weill Cornell Medicine, New York, New York, United States
  • Flombaum, Carlos D., Memorial Sloan Kettering Cancer Center, New York, New York, United States
Introduction

Patients with MM often do not have a myeloma-defining disease, and delayed recognition/treatment of a monoclonal gammopathy of renal significance (MGRS) may confer worse renal outcome.
Here we report 3 patients with “masked” LCPT (one also had FSGS) and a 4th patient with both FSGS and LCPT. None had crystalline deposits. All 4 patients had a history of untreated, smoldering MM and the initial kidney biopsy interpretation in 3 of the cases reported no evidence of MGRS. Treatment of the underlying MM resulted in improvement of renal parameters in all, suggesting MM as the etiology for the renal disease.

Case Description

73 y/o, worsening renal function (WRF), albuminuria and monoclonal proteinuria (MP). Biopsy: FSGS. Initial immunofluorescence (IF) was negative. Re-examination after protease digestion 6 months later: LCPT. Therapy for MM resulted in decreasing free light chains (FLCs), improvement of renal function, and decreased albuminuria and MP.

72 y/o, WRF and albuminuria. Biopsy: FSGS and LCPT attributed to MM. Therapy for MM resulted in decrease in FLCs, stabilization of renal function and decreased albuminuria.

75 y/o, WRF and heavy MP. Biopsy: diabetic nephropathy with interstitial inflammation. IF was negative. Following autologous stem cell transplant for progression to symptomatic MM, there was a striking improvement in FLCs, renal function and MP.

73 y/o, WRF, heavy MP and Fanconi’s syndrome. Biopsy: mild glomerulomegaly and focal sparse lymphocytic infiltrates. Initial IF was negative. Re-examination after protease digestion 6 months later: LCPT. Therapy for MM resulted in decreasing FLCs, improvement of renal function and a marked decrease in MP.

Discussion

FSGS has been rarely linked to MM. In view of the connection between treatment of the MM and improvement of the renal parameters, FSGS must be considered as an additional MM-related MGRS. The presence of monoclonal light chains (LCs) in the tubular epithelial cells (TECs) should raise the possibility of this diagnosis. Because monoclonal LCs deposits in TECs may not be detectable by standard IF techniques (“masked” LCPTs), paraffin IF after protease digestion should always be performed in kidney biopsies of patients with monoclonal gammopathies. In addition, detailed EM examination of the tubules is essential to identify the lysosomal abnormalities typical of LCPT.