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Smith-Magenis Syndrome
Sunday, 15 August 2004
Sunday, 15 August 2004

What

Smith-Magenis Syndrome (SMS) is a rare genetic disease that results in distinctive facial features, behavior problems and some mental retardation. Proper diagnosis of SMS is sometimes delayed because it can be mistaken for other diseases such as Down Syndrome or Autism.

Who

SMS occurs in about 1 out of every 25,000 births, and it affects boys and girls equally. It has been diagnosed in people around the world in all ethnic groups.

Signs and Symptoms

People born with SMS have unique facial features, which help doctors to diagnose this rare disease. These features include flattening and smallness of the middle of the face, a broadening of the bridge of the nose (between the eyes), and a shortening of the head. They may also have a distinctive shape to their mouths with a prominent chin and a full upper lip giving what has been described as a “tented” appearance, as well as deeply-set up-slanted eyes, and a deepened hoarse voice. These features may be evident at birth, but it is more common that they become more pronounced as the child ages. In a few cases, heart defects, kidney defects, and thyroid defects have been found in people with SMS. As they get older, about 2/3 of children with SMS begin to develop behavioral problems including trouble sleeping and self-injury behaviors such as pulling out their fingernails, banging their head, and inserting various objects into their ears and mouth. Often they also show a characteristic upper arm movement (“self-hugging behavior”) that becomes more exaggerated when they are happy or over stimulated. People with SMS usually have some degree of mental deficiency varying from mild to severe mental retardation. They also may have hearing loss, hyperactivity, and delay in learning to speak.

Possible Causes

SMS results when a few of the genes on chromosome 17 are missing (or deleted). Like the other chromosomes, chromosome 17 has many genes on it. Each of these genes has a specific set of jobs to do in the body to make sure that all the body’s functions run smoothly. When mistakes occur in the chromosomes and genes get lost, the jobs that those genes are responsible for cannot be performed normally. In SMS, the missing genes are thought to cause all the physical and behavioral symptoms shown by people with this disease.

Diagnosis

A diagnosis of SMS can be suggested by the distinctive facial features and the unique behaviors characteristic of this disease. However, a definitive diagnosis of SMS requires a DNA test called FISH to identify the missing genes on chromosome 17.

Treatment

Because replacing the missing genes is not possible, there is no cure for Smith-Magenis Syndrome, but there are treatments to help with the symptoms. Treatments for the behavioral symptoms of SMS include speech therapy to help with language development and behavioral therapy to help minimize outbursts. In some cases, certain medications may help with attention and focus, and other medications (melatonin) may help control the sleeping difficulties.

Prognosis

While there is no cure for SMS, most people live well into adulthood. The lifespan for any particular SMS patient depends on whether or not there are any heart, kidney, or thyroid problems. The mental retardation and behavioral problems will remain throughout the person’s lifetime.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

SMS Foundation
The site is from England and contains a list of physical features and behavioral symptoms.

SMS Contact a family
This site, also from England, is more extensive with a parent support section and additional links. S

Special Child
This site begins with the same information as the above sites, however this site has personal stories from families living with a child with SMS.

Google Search for Smith-Magenis Syndrome

References and Sources

1. GeneReviews website (www.geneclinics.org) keywords ‘Smith-Magenis’ 2. OMIM website (www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=OMIM) keywords ‘Smith-Magenis’ 3. Emery and Rimoin's Principles and Practice of Medical Genetics, 4th Edition, pages 1015-1016, 2002. 4. Syndromes of the Head and Neck (Oxford Monographs on Medical Genetics) Robert J., D.D.S., M.S., D.Sc. Gorlin, pages 107-108, 2001.