As of the year 2001, studies have shown that perlecan helps keep cartilage and bone strong and are essential for certain chemical processes in the muscle tissue. However, it has an important job in the cells of the body's connective tissue (bone, cartilage, muscles, ligaments, tendons and blood vessels). The function of the perlecan protein is not completely understood. A gene in this region, named HSPG2, makes a protein called perlecan that is thought to play the primary role in causing SJS. Genetic studies of many families revealed that all cases of SJS were linked to an area on chromosome one, described as 1p36.1. Consanguineous relationships were seen in some families. Parents have been reported to have more than one affected child. Parents of affected individuals rarely show any signs or symptoms of SJS. This was concluded after the following observations were made. spondylo-epimetaphyseal dysplasia with myotoniaīoth types of SJS are known to be inherited in an autosomal recessive manner.myotonic myopathy, dwarfism, chrondrodystrophy, and ocular and facial abnormalities.Persons with SJS Type 1A have a much longer life expectancy, although this depends on how their disease progresses. These problems may be fatal in early infancy. Respiratory and feeding difficulties are frequent with SJS Type 1B due to the more severe nature of the muscle and bone disease. However, the myotonia may lead to poor speech articulation and drooling so that affected individuals are sometimes misdiagnosed as having mental retardation. Persons affected with SJS often have normal intelligence, although varying degrees of mental retardation may affect as many as 25% of patients. These features are also due to the stiffness of the muscles that support the face and individuals with SJS appear to have a fixed facial expression. Unique facial features of SJS include narrow eye openings with drooping eye lids, a small mouth, and puckered lips. Abnormal bone shape and poor bone growth result in decreased total height, incorrect arm and leg postures, as well as curving of the spine ( scoliosis ). In addition to muscle problems, the bones in the skeleton do not develop normally and this is why SJS may also be called a type of skeletal dysplasia. The myotonia causes many joints in the body to stay in a bent or flexed position (joint contractures). The muscles tend to be quite stiff and are unable to relax normally. Both types of SJS involve generalized disease of the muscles called myopathy. Type 1B is less common but more severe and its symptoms are present at birth. Type 1A is the classical form that develops in early childhood, usually between the first and third year of life.
Descriptionįirst described in 1962, SJS is now a clearly defined syndrome that is divided into two types. Schwartz-Jampel syndrome (SJS) is a rare, inherited condition of the skeletal and muscle systems that causes short stature, joint limitations, and particular facial features.
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