Myopathy in primary systemic amyloidosis.

Involvement of the peripheral nervous system by amyloidosis is common. It is less well recognized that amyloid can directly infiltrate and weaken skeletal muscle. We report a case of a 73-year-old woman, known to have cardiac amyloidosis, who developed profound weakness secondary to amyloid myopathy. Review of the 8 other well documented cases in the literature has revealed a rather homogeneous syndrome. Proximal weakness, muscle stiffness, pseudohypertrophy and myalgia constitute the principal features. This syndrome usually develops in cases with well recognized generalized amyloidosis. Amyloid is deposited within the basal lamina of blood vessels and muscle fibers.