Rinshō shinkeigaku = Clinical neurology
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A 78-year-old man presented with subacute progressive proximal weakness and dysphagia. A biopsy specimen from the left biceps femoris revealed evidence of necrotic and regenerating muscle fibers, but lymphocyte infiltration was not noted. The patient was diagnosed with necrotizing myopathy with anti-signal recognition particle (SRP) antibodies. ⋯ Immunoelectrophoresis of serum revealed IgG M protein, and muscle pathology revealed amyloid deposits in numerous blood vessels and at the periphery of a few muscle fibers, and deposits stained positive for anti-λ light chain antibody. The patient was diagnosed with amyloid myopathy, and therapy for systemic amyloid light chain amyloidosis caused muscle weakness to diminish. Amyloidosis is believed to be the primary pathology in this case based on the patient's response to treatment reaction, but the significance of a case involving both amyloid myopathy and necrotizing myopathy warranted examination.