Free light measurement identifies relapse and prompts to reconsider amyloid typing in a patient with AL amyloidosis

The detection and quantification of amyloidogenic light-chains (LC) is necessary for diagnosis and evaluation of response in AL amyloidosis. A 69 years old woman was initially diagnosed, in another center, with AL-λ amyloidosis with renal and soft tissue involvement in December 2001. After 4 cycles of therapy with melphalan and dexamethasone serum and urine immunofixation were negative and, after cycle 6, complete remission was confirmed. Free light chain (FLC) ratio was normal until June 2006, when proteinuria increased, and an elevated κ-FLC concentration with abnormal κ/λ-ratio was documented. We repeated the abdominal fat aspirate for amyloid typing by immune-electron microscopy that revealed κ-LC deposits. The diagnosis was AL-κ. A relapse was documented and the patient was started on bortezomib and dexamethasone therapy. After 8 cycles, complete remission was obtained. In this case, FLC allowed the identification of the amyloidogenic-LC, enabling the detection of relapse.