Schwartz–Jampel syndrome (SJS) is a rare disorder that is characterised by myotonia and skeletal abnormalities.

SJS is caused by mutations in the HSPG2 gene encoding the protein perlecan. Myotonia results in a fixed facial expression with blepharophimosis, microstomia, pursed lips and mask-like faces. The typical skeletal and other abnormalities include short stature, kyphoscoliosis, joint contractures, and micrognathia. Tracheal intubation is difficult in these patients because they have micrognathia, cervical kyphoscoliosis, and a limited mouth opening.