Schwartz–Jampel syndrome (SJS) is a rare disorder, characterized by the development of osteochondrodysplasia and myotonia. It is primarily inherited in an autosomal recessive pattern.
Schwartz-Jampel syndrome, otherwise referred to as chondrodystrophic myotonia or myotonic myopathy, causes muscle hypertrophy, stiffness, and weakness at a very young age, usually either immediately after birth or within the first year of an infant's life [1].
Limb flexion is restricted and is usually the first sign for which parents seek medical care. Infants also display a delay in development of motor abilities : walking is achieved significantly later in comparison to healthy individuals. However, children affected by SJS eventually attain the ability to walk and become self-reliant.
At an older age, patients report considerable joint flexion limitations and stiffened muscles, a symptom that is particularly experienced in the quadriceps. The syndrome also induces various skeletal irregularities, such as micrognathia, pectus carinatum, kyphosis, coxa valga, short femoral bones and a short neck [2]. The outer appearance of individuals affected by SJS is also dysmorphic: blepharophimosis with blepharospasm, flattened facies, eyelid hypertrichosis, and micrognathia. Defective capital femoral epiphyses is another sign associated with Schwartz-Jampel syndrome [3]. As far as the cognitive development of these individuals is concerned, the majority of SJS patients display normal intelligence, although mental disabilities may occur in up to 20% of the cases. SJS patients with significantly high intelligence are thought to be nonexistent.
Depending primarily on the age of onset, SJS is further classified into two categories: SJS1 and SJS2. SJS type 1 produces the initial symptoms approximately during childhood, whereas SJS type 2 is a congenital and rare sub-type of Schwartz-Jampel syndrome [4]. Schwartz-Jampel syndrome type I is further divided into two sub-categories, IA and IB, with the latter manifesting earlier in the course of the patient's life with more severe symptoms.
A detailed medical history including the symptoms for which the parents initially sought medical advice is pivotal for the diagnosis of Schwartz-Jampel syndrome. Parents typically report a difficulty flexing an infant's joints, hypertrophic muscles and mobility issues. A careful clinical examination will reveal signs related to SJS, such as myotonia, kyphosis, joint flexion restriction, blepharospasm, coxa valga, hypertrichosis of the eyelids and a general difficulty to perform basic movements.
The clinical findings can be validated by imaging modalities, such as radiographs that will illustrate kyphosis or shorter femoral bones [5]. Imaging modalities, however, contribute little to the final diagnosis. Blood tests are also of limited use: mild augmentation of creatine kinase in the serum or aldolase may be detected, findings which do not clearly suggest SJS. Genetic testing is available, but not on a commercial basis. Families, should, therefore, be referred to specialty referral centers that research the disease's genetic basis.
No specific findings or abnormalities on histological examination have been noted in SJS. A muscle biopsy is usually compatible with a myopathy. Lastly, electromyography and nerve conduction studies have been employed to rule out the differential diagnosis, but their findings are usually normal [5] [6].