Light chain (AL) amyloidosis is caused by a usually small plasma cell (or B cell) clone. In the last two decades the ability of reliably detecting and measuring the amyloid monoclonal protein and biomarkers of organ damage radically changed the management of this disorders.
The measurement of circulating free light chains coupled with immunofixation of serum and urine is needed to identify the amyloid light chain at diagnosis, to assess response to treatment, and to identify relapse. More recently, evaluation of minimal residual disease in the bone marrow by next generation flow cytometry has been introduced.
Staging is based on markers of cardiac (NT-proBNP, troponin) and renal (proteinuria, eGFR) involvement, whose changes are used to evaluate response to treatment. These biomarkers have also been proposed to allow early pre-symptomatic diagnosis in patients known to have a plasma cell dyscrasia. Other biomarkers of organ dysfunction and damage, such as GDF-15, ST2, urinary albumin to creatinine ratio have been proposed. The clinical laboratory has a crucial role in screening, diagnosing, staging, and monitoring systemic AL amyloidosis.