骨格筋でのみアミロイドの沈着を確認しえたアミロイドーシスの1例

Abstract

A 75-year-old man was admitted to our hospital with progressive weakness in the lower extremities for 7 months. Immunoelectrophoresis of serum detected IgA λ type M protein and bone marrow examination detected an increase in monoclonal plasma cells, thus leading to a diagnosis of IgA λ type multiple myeloma. Subsequent muscular CT scan showed severe fatty infiltration of vastus lateralis muscles, and histopathological examinations of biopsied muscle specimens an abundance of abnormal "ring-fiber-like" appearance, positive staining by Congo red and the presence of anti-λ light chain antibody. This led to a diagnosis of amyloid myopathy. No depositions were seen in rectal mucosa, cardiac muscle, or sural nerve. The results of double immunohistochemical staining using anti-dystrophin antibody and anti-λ light chain antibody suggested the possibility of direct injury by amyloid to muscle fibers. The case presented here was thus amyloidosis confirmed by deposition of amyloid only in muscles. In conclusion, when amyloidosis is suspected and there is evidence of muscle injury, muscle biopsy should be performed.