Schwartz-Jampel syndrome (SJS) is a rare genetic disorder characterized by abnormalities of the skeletal muscles, including muscle weakness and stiffness (myotonic myopathy); abnormal bone development (bone dysplasia); permanent bending or extension of certain joints in a fixed position (joint contractures); and/or growth delays resulting in abnormally short stature (dwarfism). Affected individuals may also have small, fixed facial features and various abnormalities of the eyes, some of which may cause impaired vision. The range and severity of symptoms may vary from case to case. Two types of the disorder have been identified that may be differentiated by age of onset and other factors. Schwartz-Jampel syndrome type 1, which is considered the classical form of the disorder, may become apparent during early to late infancy or childhood. Schwartz-Jampel syndrome type 2, a more rare form of the disorder, is typically recognized at birth (congenital). Most researchers now believe that SJS type 2 is actually the same disorder as Stuve-Wiedemann syndrome and not a form of Schwartz-Jampel syndrome. (For more information on Stuve-Wiedemann syndrome see the Related Disorders section of this report.)
Schwartz-Jampel syndrome is thought to be inherited as an autosomal recessive trait. However, some cases reported in the medical literature suggest an autosomal dominant inheritance pattern.