Clonal biomarkers for diagnosis and response to treatment assessment in light chain amyloidosis: The role of the laboratory

Serum monoclonal components, Bence-Jones proteinuria (PBJ) and free light chains (FLC) are clonal biomarkers for diagnosis and response assessment in light chain (AL) amyloidosis. Two clinical reports are presented here to illustrate the utility of these biomarkers. The first case is a patient with AL êappa renal amyloidosis. Serum and urine immunofixation were negative and the FLC ratio was abnormal. Immunoelectron microscopy on tissue biopsy was negative. Amyloid typing was achieved by mass spectrometry on fat pad aspirate. The second case is a patient with AL cardiac amyloidosis with PBJ lambda and low concentration of amyloidogenic FLC (32 mg/L). Urine capillary electrophoresis was used to assess response to treatment. The progressive reduction of PBJ after treatment was accompanied by reduction of NT-proBNP and improvement of clinical conditions. Clonal biomarkers are irreplaceable tools in management of AL amyloidosis. There is a need for more sensitive techniques for identification of monoclonal FLC on serum and urine.