Intranuclear rods in severe congenital nemaline myopathy

We compared the muscle pathology and clinical course in eight patients with congenital nemaline myopathy. An abundance of large intranuclear rods was present in the muscle fibers of one patient with a rapid, fatal course. Intranuclear rods were not present in the muscles of seven patients with a benign course. The large intranuclear rods and the smaller sarcoplasmic rods were similar ultrastructurally and exhibited positive immunoperoxidase staining with anti-alpha-actinin antibodies. The accumulation of alpha-actinin within myonuclei may reflect a severe disturbance of normal intracellular processes regulating myofibrillar synthesis. Since two previously reported infants with intranuclear nemaline rods also had a fatal outcome, the presence of intranuclear rods may represent a marker for a severe form of congenital nemaline myopathy.