Part I. Amyoplasia: a common, sporadic condition with congenital contractures.

A specific congenital contracture (arthrogryposis) syndrome has been recognized in 135 out of 350 patients with various kinds of congenital contractures. This sporadic syndrome, designated amyoplasia is characterized by absence of limb muscles that are replaced by fibrous and fatty tissue. At birth there is characteristic positioning of the limbs with internal rotation at shoulders, extension at elbows, and flexion of the hands at the wrists. Severe equinovarus deformities of the feet are usually present. Contractures at knees and hips occur in a variety of positions. Typically, the face is round with a frontal midline capillary hemangioma and slightly small jaw. Intelligence is normal. Approximately 63% of our patients had involvement of four limbs (almost always symmetrically), 24% mainly of lower limbs, and 13% mainly upper limbs. Typically, no other malformations are present. However, minor anomalies are seen often, and include hypoplastic digits and hypoplasia of scrotum or labia, the umbilical cord may be wrapped about a limb at birth. In utero fetal activity is decreased and breech delivery is increased in amyoplasia. All cases were sporadic; identical twins are discordantly affected.