Hereditary ptosis.

Weakness of the external eye muscles was believed to be of genetic origin in 94 of 97 patients studied and was familial in 73 patients. Thirty patients had congenital ptosis alone or with weakness of other ocular muscles. The lack of progression and high incidence of other congenital anomalies suggested that congenital ptosis had in most instances a development etiology. Neurogenic congenital ptosis was documented in one instance and was suspected in another patient. The most common causes of progressive ophthalmaplegia with onset after birth was myotonic dystrophy and ocular muscle dystrophy. On clinical and genetic grounds, ptosis associated with retinitis pigmentosa was considered as a distinct disease and there was no conclusive evidence that ocular muscle dystrophy and oculopharyneal dystrophy were separate diseases. The relatively high incidence of familial myasthenia gravis was probably due to the selection of the patients. Two pairs of sibs with "chondrodystrophic myotonia" were included in the study. Progressive external ophthalmoplegia with onset after birth was neurogenic in three instanced. It accompanied motor neuron disease, Kugelberg-Welander disease and an undertermined disease affecting the central and peripheral nervous system, each in one patient.