Managing Systemic Light-Chain Amyloidosis

Abstract

Amyloidosis is a rare disease in which a specific protein is deposited as aggregated interstitial fibrils that can compromise organ function and lead to death. Immunoglobulin (Ig) light-chain amyloidosis (AL), caused by the monoclonal gammopathy of a plasma cell dyscrasia, is the most common type. A hereditary type is also caused by mutant transthyretin and other proteins. Rarely, a patient with amyloid has both a monoclonal gammopathy and a hereditary protein. In AL, circulating monoclonal Ig light chains can be measured with the free light-chain (FLC) assay and provide a target for therapy to eliminate the underlying plasma cell dyscrasia while supporting the patient's organ function. Amyloid deposits can be resorbed and organ function restored if the amyloid-forming precursor FLC is eliminated. For patients with limited organ involvement, intravenous melphalan in doses from 100 to 200 mg/m2 with autologous stem cell support (SCT) is an effective approach and, when followed at 3 months post-SCT with adjuvant thalidomide and dexamethasone for persistent plasma cell disease, has a 1-year hematologic response rate of 77%. Monthly oral melphalan and dexamethasone for 1 year can also be effective therapy for patients too sick for SCT (67% response rate). Hematologic complete responses are usually durable and result in long-term survival and a variable degree of organ recovery. For patients with advanced cardiac involvement, the prognosis remains guarded even with treatment. Drugs effective in multiple myeloma are usually active in AL, depending on side effects. New agents such as bortezomib and lenalidomide have shown promising activity, and novel antibody-based approaches for imaging amyloid and accelerating removal of deposits are being actively investigated.