Schwartz-Jampel Syndrome (Chondrodystrophic Myotonia)
Schwartz-Jampel syndrome is an autosomal-recessive disorder with myotonia, dwarfism, diffuse bone disease, narrow palpebral fissures, blepharospasm, micrognathia, and flattened facies (see Fig.
12.10). Onset is usually before age 3. Patients have respiratory and feeding difficulties with impaired swallowing. Limitation of joint movement may be present along with skeletal abnormalities, including short neck and kyphoscoliosis. Muscles are typically hypertrophic and clinically stiff. There is a characteristic facies with pursed lips, micrognathia, and small mouth. Patients may be difficult to intubate. Ocular changes include myopia and cataracts. There may be hirsutism and small testes. The symptoms are not progressive. The protein perlecan with gene loci at chromosome 1p34- p36 has been implicated.Electrodiagnostic studies show continuous electrical activity, with electrical silence being difficult to obtain. There is relatively little waxing and waning in either amplitude or frequency of complex repetitive discharges. Abnormal sodium channel kinetics in the sarcolemma of muscle has been demonstrated. Some therapeutic benefit has been reported with procainamide and carbomezapine.
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