Amyloid-Associated Muscle Pseudohypertrophy

Abstract

• The case of a patient with progressive enlargement and induration of muscles owing to amyloid infiltration is presented. The presence of free λ chains in serum and urine as well as plasmacytosis in the bone marrow suggested primary amyloidosis. Although the amyloid accumulated outside the sarcolemma, electromyographic findings and the presence of diffuse extrajunctional acetylcholine receptors suggest that the amyloid interfered with normal propagation of action potentials along the sarcolemmal membrane.