Schwartz-Jampel syndrome (SJS, chondrodystrophic myotonia) is a rare autosomal recessive disease defined by myotonia, skeletal abnormalities, facial deformities, and delayed growth. Presentation is variable. It has 2 forms: SJS type 1 and SJS type 2. SJS type 1 is caused by HSPG2 gene mutations. SJS type 2 is caused by a mutation in the LIFR gene; many now consider this to be the same disease as Stuve-Wiedemann syndrome. SJS type 2 has a more severe phenotype than type 1 and most commonly affects individuals from the United Arab Emirates. Depending on the type, clinical signs may be apparent soon after birth or may not be recognized until infancy or age 2. The disease will typically stabilize after adolescence.

Most patients with SJS type 1 will have bone abnormalities and chondrodystrophy that may be recognized at birth or noticed by age 2. Additional skeletal malformations may include myotonic myopathy, small skeletal muscles, joint contractures, hip dysplasia, kyphoscoliosis, and pectus carinatum. Infants may have normal or low birth weight, and growth rate will usually fall below normal range within the first and second year of life. Patients may also experience delayed motor development that usually improves after age 2. Mental development is typically normal. Patients usually experience abnormally short stature into adulthood (dwarfism).

SJS type 2 patients are distinguished by unique facial abnormalities, muscle weakness, skeletal abnormalities, bowing of the limbs, and short stature. Joint contractures at birth may also occur. In severe cases, infants may have hyperthermia and trouble feeding, swallowing, and breathing, which may lead to life-threatening complications.

Treatment should be individualized to each patient and their specific symptoms and may require a multidisciplinary approach. Therapy is supportive and symptomatic. Early intervention is essential. Genetic counseling may be beneficial for affected patients and family.