European Collaborative Study Defining Clinical Profile Outcomes and Novel Prognostic Criteria in Monoclonal Immunoglobulin M–Related Light Chain Amyloidosis

PurposeImmunoglobulin M (IgM)–related light chain (AL) amyloidosis, which accounts for 6% to 10% of all AL amyloidosis cases, is a rare and poorly studied clinical entity. Its natural history and management is not clearly defined. Prognostic and response criteria for AL amyloidosis in general have not been validated in this population.Patients and MethodsWe retrospectively gathered data for 250 patients diagnosed with IgM AL amyloidosis from three European amyloidosis centers. Clinical features, hematologic response, and overall survival (OS) were analyzed. The current staging and response criteria in non-IgM AL amyloidosis was applied to this series to assess its utility in this patient cohort.ResultsPatients with IgM AL amyloidosis have a significant IgM paraprotein (median, 10 g/L), less frequent lambda light chain isotype, and evaluable difference between involved and uninvolved free light chains (dFLCs; > 50 mg/L) in only two thirds of patients. Bone marrow showed clear non-Hodgkin lymphoma as the un...