Congenital myopathy with myasthenic features and congenital cataract in two siblings.

Two siblings with congenital myopathy showing myasthenic manifestations together with congenital cataract are reported. Their muscle weakness fluctuated and was alleviated by edrophonium chloride. Their serum creatine kinase activity was elevated, and the waning phenomenon was observed on repetitive nerve stimulation. Biopsied muscle showed degenerative changes with type 1 fibre predominance and abnormal morphology of neuromuscular junctions.