However, the tests resulted inadequate for the majority of patients with AL amyloidosis and more than 3% of patients with nonsecretory (NS), oligo-secretory (OS), and light chain (LC) multiple myeloma. These measurements were sufficient for most MGUS and MM patients.
The diagnosis and evaluation of PC dyscrasias have been performed, until the early 2000s, using both the protein electrophoresis (PEP) and immunofixation electrophoresis (IFE) of serum and urine, representing the gold standard. On the contrary, a significantly abnormal κ/λ rFLC is usually due to plasma cell (or lymphoproliferative) disorders that secrete only one type of FLC in excess and disturb the normal balance between κ and λ secretion. The kappa/lambda (κ/λ) FLC ratio (rFLC), however, usually remains normal in these conditions. Abnormal concentrations of kappa (κ) and lambda (λ) FLC may result from a number of clinical situations including immune suppression, immune stimulation, reduced renal clearance, or monoclonal plasma cell proliferative disorders. Serum concentrations of free light chains (sFLC) are dependent on the balance between production and renal clearance. Malignant plasma cell clones overproduce and secrete a “monoclonal M-protein” (MP), an abnormal complete monoclonal antibody or its fragment, called light chain (LC).
Plasma cell (PC) dyscrasias represent a spectrum of progressively more severe monoclonal gammopathies. We present four clinical cases where sFLC allowed diagnosis of extramedullary relapse during treatment. In real life, we cannot always evaluate disease progression with measurable MC, but we can increase the accuracy by using serum free light chain (sFLC) assay.
Multiple myeloma remains incurable with frequent aggressive relapse.