The contribution of the plasma free light chains determination to the diagnosis of the Light Chain Deposition Disease

Light Chain Deposition Disease (LCDD) is a clinical condition characterized by renal deposition of monoclonal free light chains, produced by B-cells or plasma cell clone. In LCDD, non-organized monoclonal immunoglobulin deposits along the glomerular and tubular basement membranes are composed of monoclonal light chains (kappa isotype in 92% of cases). These deposits differ from amyloidosis deposits because they do not show the typical affinity for Congo Red and do not have a fibrillar organization. We described a 64 years male patient with hypertension, proteinuria and nephrotic syndrome. Plasma cell dyscrasias diagnostic work-up evidenced only an abnormal kappa/lambda ratio and increased plasma concentrations of kappa free light chains. Serum and urine immunofixation did not demonstrated the presence on monoclonal immunoglobulin. Kidney biopsy showed a membranoproliferative glomerulonephritis pattern and renal immunofluorescence demonstrated the parietal diffuse linear staining of kappa monoclonal light chain along basement membranes. Ultrastructural appearance confirms the diagnosis of LCDD.