Serum free light chain assays for monitoring response to treatment in a patient with pharmacoresistant light chain multiple myeloma

We describe the case of a 78 year old man admitted to the Nephrology ward with strangury. Laboratory tests showed proteinuria with preserved renal function. Serum and urine immunofixation showed a faint monoclonal λ band, while serum free light chain (FLC) assays (Freelite, The Binding Site) resulted in an abnormal κ/λ ratio, confirming the presence of a λ FLC monoclonal component. After bone marrow examination, the diagnosis was stage IIA λ light chain multiple myeloma. The patient started bortezomib, melphalan and prednisone treatment. In the following days, λ FLC concentrations still remained elevated indicating therapy failure. A week later, the patient became anuric and laboratory tests showed a pattern of acute renal failure and increased serum λ FLC concentrations. The patient started a new treatment with bicarbonate, mannitol and dexamethasone, but therapy was not effective again and λ FLC concentrations resulted persistently high and associated with anury. Clinicians decided to suspend pharmacological therapy and to dialyze the patient. FLC assay was performed every two hours to monitor FLC removal. After six sessions of hemodialysis, λ FLC concentrations decreased, diuresis was restored and renal function improved. Myeloma treatment was re-initiated with steroids and, after kidney recovery, dialysis was suspended. In this case, FLC assays helped to confirm myeloma suspicion, to define the most effective therapy and to assess the response to treatment