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Smith-Magenis Syndrome (SMS)

What is Smith-Magenis syndrome (SMS)?

Smith-Magenis syndrome (SMS) is a developmental disorder that affects multiple organ systems of the body. It is characterized by a pattern of abnormalities that are present at birth (congenital), as well as behavioral and cognitive problems.

What are the symptoms of Smith-Magenis syndrome (SMS)?

  • Mild to moderate intellectual disability
  • Delayed speech and language skills
  • Broad, square-shaped face with deep-set eyes and prominent jaw
  • Sleep disturbances
  • Behavioral issues

Other, less frequent symptoms include:

  • Short stature
  • Scoliosis
  • Reduced sensitivity to pain and temperature
  • Hoarse voice
  • Ear abnormities leading to hearing loss
  • Vision problems 

What causes Smith-Magenis syndrome (SMS)?

Most people with Smith-Magenis syndrome have a deletion of genetic material from a specific region of chromosome 17. The loss of one specific gene – the retinoic acid induced 1 or RAI1 – is responsible for most of the characteristic features of SMS.

A small percentage of people with SMS have just a mutation in the RAI1 gene (not a deletion of the larger part of the chromosome). 

How is Smith-Magenis syndrome (SMS) diagnosed?

The diagnosis of SMS is confirmed when deletion 17p11.2 or RAI1 gene mutation is identified. This diagnosis is reached after identification of characteristic symptoms, a detailed patient and family history, a thorough clinical evaluation, and a variety of genetic tests.

Specialized exams include:

  • Fluorescent in situ hybridization (FISH)
  • Chromosomal microarray analysis
  • Chromosomal study known as G-band analysis
  • Molecular genetic testing

What treatments are available for Smith-Magenis syndrome (SMS)?

There is currently no cure or direct treatment for SMS, only symptom management.

Services that may be beneficial include special remedial education, speech/language therapy, occupational therapy, and sensory integration therapy.

Where can I find out more about Smith-Magenis syndrome (SMS)?

Smith-Magenis Syndrome (SMS) Articles