Light Chain Disease: A Diagnostic Challenge

Light-chain multiple myeloma (LCMM) is a rare subtype of multiple myeloma (MM) that can affect various organs, with the kidneys being the most commonly impacted. LCMM typically has a more aggressive progression and is associated with a poorer prognosis. Renal dysfunction in LCMM arises due to the buildup of monoclonal immunoglobulin light chains in the kidneys. In this case, we present a 40-year-old male who came in with generalized swelling, decreased urine output, severe anaemia, and significant renal impairment. He underwent five sessions of haemodialysis and received five units of blood transfusion. Initial screening to exclude plasma cell neoplasm by serum protein electrophoresis showed negative results for monoclonal band. But bone marrow examination revealed an abundance of atypical plasma cells, constituting about 80% of the sample. Immunophenotyping identified 70% clonal plasma cells, with a positive lambda light chain marker. Urine analysis confirmed the presence of free light chains. Quantitative immunofixation markedly higher ratio of involved free light chain (instead of Kappa lambda ratio) but heavy chain level is within normal range. A CT scan indicated subtle changes in the axial and proximal appendicular skeleton. Early diagnosis of LCMM is crucial to initiate timely treatment.