amyotonia congenita

1. atonic pseudoparalysis of congenital origin (neither familial nor hereditary), observed especially in infants and characterized by absences of muscular tone only in muscles innervated by the spinal nerves. Syn: congenital atonic pseudoparalysis, myatonia congenita, Oppenheim’s disease, Oppenheim’s syndrome.

2. an indefinite term for a number of congenital neuromuscular disorders that cause generalized myotonia in young children, and that have a benign course (static or regressive).