Plasmapheresis for Treatment of Light Chain Amyloidosis Related Myopathy

Background: Light chain (AL) amyloidosis is a plasma cell disorder characterized by abnormal fibrillary light chain deposition causing cardiac, renal, hepatic, gastrointestinal and peripheral nervous system dysfunction. Muscle disease occurs in 1.5% of individuals causing progressive proximal weakness thus far considered untreatable. Methods: We reviewed two cases of AL amyloidosis associated myopathy at our institution who had robust response to plasmapheresis. Both were at stringent clinical response following CyBorME therapy during peak severity of their myopathy. Results: In case 1, a 70-year-old male with recently diagnosed kappa light chain multiple myeloma and cardiac/renal amyloidosis developed severe subacute proximal weakness preventing ambulation. CK was normal and electromyography was consistent with irritable myopathy. Deltoid biopsy showed perimysial and endomysial amyloidosis. A trial of plasmapheresis in a tapering schedule resulted in robust recovery of strength. In case 2, a 67-year-old female with recently diagnosed kappa light chain multiple myeloma with amyloidosis on fat pad aspirate developed severe subacute proximal weakness requiring prolonged hospital admission. CK was normal and electromyography demonstrated non-irritable myopathy. Bicep biopsy showed perivascular amyloidosis. A trial of plasmapheresis in a tapering schedule resulted in robust recovery of strength. Conclusions: Plasmapheresis is a novel and potentially effective treatment for patients with AL amyloidosis associated myopathy.