Three patients with congenital inflammatory myopathy are reported from the Montreal Children's Hospital and Neurological Institute McGill University, Montreal, Canada. Seven additional cases are reviewed from the literature. The essential criteria for diagnosis were 1) antenatal or neonatal presentation with decreased fetal movements, muscular hypotonia and weakness with or without arthrogryposis, and 2) muscle biopsy evidence for inflammatory cell infiltrate and muscle fiber damage. CPK is elevated and the EMG is myopathic. CNS involvement was present in six of the patients. Two died, one at nine months and the other at five years. Treatment with steroids was used in 7 of the 10 patients with variable results. Possible etiologies included intrauterine viral infection or an autoimmune process. 
COMMENT: Congenital inflammatory myopathy is a rare cause of the “floppy infant syndrome”, and the differential diagnosis includes a congenital muscular dystrophy syndrome of Fukuyama or Walker-Warburg. Fukuyama's congenital muscular dystrophy includes hydrocephalus, ocular manifestations and mental retardation and Walker-Warburg's syndrome is characterized by lissencephaly and retinal abnormalities. Treatment of the cases of congenital inflammatory myopathy with steroids may improve motor development but does not result in intellectual improvement.