[Motor impairment in amyloid-associated muscle pseudohypertrophy].

Muscle involvement, usually associated with pseudohypertrophy, has been described very rarely in patients with AL-(primary or myeloma-associated) amyloidosis. Although precise mechanisms for the motor impairment in amyloid-associated muscle pseudohypertrophy are unknown, amyloid accumulation in the muscle has been thought to be a main cause of muscle weakness. We here describe a patient of amyloid-associated muscle pseudohypertrophy with IgA lambda plasma cell dyscrasia, and discuss possible mechanisms for the physical disability. The patient, a 65-year-old man, was admitted because of progressive stiffness of limb and bulbar muscles for approximately three years. On physical examination he appeared muscular and athletic. The muscles were firm with wooden or rock-like hardness. Superficial veins were engorged in all extremities. Macroglossia was marked. Resistance to passive movement was noted in all extremities with decreased range of motion; proximal joints were more severely affected. The patient walking for a short distance, his legs became heavy, tired and firm, which forced him to stop. Immunoelectrophoresis revealed the monoclonal secretion of IgA lambda in the serum and free lambda light chain in the urine. Bone marrow examination disclosed 30% plasma cells with a large prevalence of IgA lambda-containing cells. A bone scan showed an increased uptake of 99mTc-methylene diphosphate in the shoulder and pelvic joints. Tissue pressures of the quadriceps femoris at the supine and standing positions, and after walking were as high as 47, 89, and 112 mmHg, respectively. Venography of the left leg showed narrowing of the femoral vein and visualization of saphena magna vein.(ABSTRACT TRUNCATED AT 250 WORDS)