Lambda light chain crystalline proximal tubulopathy with probable light chain cast nephropathy and clonal plasma cell infiltrate – uncommon manifestations of a rare form of multiple myeloma

Yan-Fei Ng,Chandramouli Nagarajan,Chang-Yin Choinh,Hwai-Liang Loh,Marvin Raden Torres De Guzman

doi:10.34172/jnp.2021.08

Yan-Fei Ng, Chandramouli Nagarajan + Show 3 more

Open Access

https://doi.org/10.34172/jnp.2021.08

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Abstract

Light chain proximal tubulopathy (LCPT) is an uncommon renal disease characterized by the accumulation of monoclonal light chains within proximal tubular epithelial cells, with or without crystal formation. We report a rare case of lambda LCPT with crystals. Renal biopsy showed substantial acute tubular injury with unusual cytoplasmic changes affecting proximal tubules. In addition, abnormal tubular casts suggested concomitant light chain cast nephropathy. A clonal plasma cell infiltrate was present in the tubulointerstitial compartment. Immunofluorescence demonstrated strong staining for lambda light chain in tubular epithelial cells. Despite the absence of discernible crystals on light microscopy (LM), they were readily identified when ultrastructural evaluation was undertaken. Crystalline inclusions demonstrated positive immunogold labelling for lambda.

Highlights

Renal dysfunction is increasingly recognized in patients with monoclonal gammopathy, resulting from clonal proliferation of B-lymphocytes or plasma cells and subsequent overproduction of monoclonal immunoglobulins
The concept of monoclonal gammopathy of renal significance (MGRS) was introduced in 2012 [3] and renal manifestations of a monoclonal gammopathy can be the first signs of an underlying neoplastic hematological condition
We report a case of lambda Light chain proximal tubulopathy (LCPT) with crystals, highlighting some unusual light microscopic and ultrastructural features

Summary

Introduction

Renal dysfunction is increasingly recognized in patients with monoclonal gammopathy, resulting from clonal proliferation of B-lymphocytes or plasma cells and subsequent overproduction of monoclonal immunoglobulins. Light chain proximal tubulopathy (LCPT) is characterized by presence of monoclonal light chains within proximal tubular epithelial cells, with or without crystal formation. The myeloma screen revealed a normal serum kappa free light chain (FLC) concentration of 17.3 mg/L (3.3–19.4 mg/L) while lambda FLC was elevated at 144 mg/L (5.7–26.3 mg/L).

Results

Conclusion