Facilitating myasthenic syndrome and quadriceps myopathy.

A patient presented with myasthenic syndrome apparently not related to any neoplasia. A peculiar myopathy characterized by absolute predominance (99.50%) and atrophy of type 2A muscle fibers was found in both quadriceps muscles. It is difficult to determine the relation between the myasthenic syndrome and the localized quadriceps myopathy for which a congenital nature is suggested.