Axial myopathy due to primary amyloidosis.

A 74-year-old man presented with progressive weakness involving only his back muscles. Serum protein electrophoresis revealed the presence of a monoclonal gammopathy. Muscle biopsy of affected muscles demonstrated amyloid light chain deposition surrounding individual muscle fibers as well as in the walls of blood vessels in association with vasculitis. Selective involvement of axial muscles in isolated amyloid myopathy has not been previously described. We report the occurrence of axial myopathy with associated vasculitis as a presenting feature of primary (AL) amyloidosis. Amyloidosis should be considered in the differential diagnosis of focal myopathies, since the condition may be responsive to chemotherapy.