A follow-up study of congenital non-progressive myopathies.

To determine the development and prognosis of patients with the moderate congenital form of congenital non-progressive myopathies (CNM), we investigated 55 patients with CNM by questionnaires. This patient group included 18 with nemaline myopathy, 11 with central core disease, 3 with myotubular myopathy, 15 with congenital fiber type disproportion and 3 with minicore disease. As to motor development, almost all patients had learned to walk alone by 3 years of age, averaging 2 2/12 years. Central nervous system involvement including mental retardation was seen in 24% of the patients, predominantly in patients with myopathy. The level of mental retardation was not related to the severity of muscle weakness. Patients with central core disease had a higher frequency of skeletal deformities. CNM were not necessarily benign in their prognosis as previously thought, but sometimes showed progressive deterioration leading to death. In 16% of patients, progressive deterioration in muscle strength and respiratory function became manifest after once the patient became ambulant. Even in the benign congenital form, seven of 55 patients died from respiratory or cardiac failures by 20 years of age. Therefore evaluation of cardiopulmonary function at regular intervals is important in the continuing care of patients with CNM.