Chondrodystrophic myotonia (Schwartz-Jampel syndrome): report of a new case and follow-up of patients initially reported in 1969.

We report on a 9-year-old boy with chondrodystrophic myotonia (Schwartz-Jampel syndrome) and the progress of a brother and sister with this syndrome first described in 1969. This is an autosomal recessive trait characterized by mask-like face, narrow palpebral fissures (due to blepharophimosis, blepharospasm, and abnormal orbital configuration), microstomia, micrognathia, myotonia, muscular hypertrophy, osteochondrodysplasia, and growth retardation. Expressivity varies and in some sibships females are less severely affected than their brothers. The sexual development of the sibs with chondrodystrophic myotonia, who are now in the mid to late second decade, has been normal. Linear growth rate accelerated during puberty but the adult height of the male is less than normal. Administration of human growth hormone had no consistent effect on the growth pattern of this boy.