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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

Smith-Magenis syndrome

Reviewed December 2013

What is Smith-Magenis syndrome?

Smith-Magenis syndrome is a developmental disorder that affects many parts of the body. The major features of this condition include mild to moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems.

Most people with Smith-Magenis syndrome have a broad, square-shaped face with deep-set eyes, full cheeks, and a prominent lower jaw. The middle of the face and the bridge of the nose often appear flattened. The mouth tends to turn downward with a full, outward-curving upper lip. These facial differences can be subtle in early childhood, but they usually become more distinctive in later childhood and adulthood. Dental abnormalities are also common in affected individuals.

Disrupted sleep patterns are characteristic of Smith-Magenis syndrome, typically beginning early in life. Affected people may be very sleepy during the day, but they have trouble falling asleep and awaken several times each night.

People with Smith-Magenis syndrome have affectionate, engaging personalities, but most also have behavioral problems. These include frequent temper tantrums and outbursts, aggression, anxiety, impulsiveness, and difficulty paying attention. Self-injury, including biting, hitting, head banging, and skin picking, is very common. Repetitive self-hugging is a behavioral trait that may be unique to Smith-Magenis syndrome. People with this condition also compulsively lick their fingers and flip pages of books and magazines (a behavior known as "lick and flip").

Other signs and symptoms of Smith-Magenis syndrome include short stature, abnormal curvature of the spine (scoliosis), reduced sensitivity to pain and temperature, and a hoarse voice. Some people with this disorder have ear abnormalities that lead to hearing loss. Affected individuals may have eye abnormalities that cause nearsightedness (myopia) and other vision problems. Although less common, heart and kidney defects also have been reported in people with Smith-Magenis syndrome.

How common is Smith-Magenis syndrome?

Smith-Magenis syndrome affects at least 1 in 25,000 individuals worldwide. Researchers believe that many people with this condition are not diagnosed, however, so the true prevalence may be closer to 1 in 15,000 individuals.

What are the genetic changes related to Smith-Magenis syndrome?

Most people with Smith-Magenis syndrome have a deletion of genetic material from a specific region of chromosome 17. Although this region contains multiple genes, researchers believe that the loss of one particular gene, RAI1, in each cell is responsible for most of the characteristic features of this condition. The loss of other genes in the deleted region may help explain why the features of Smith-Magenis syndrome vary among affected individuals.

A small percentage of people with Smith-Magenis syndrome have a mutation in the RAI1 gene instead of a chromosomal deletion. Although these individuals have many of the major features of the condition, they are less likely than people with a chromosomal deletion to have short stature, hearing loss, and heart or kidney abnormalities.

The RAI1 gene provides instructions for making a protein whose function is unknown. Mutations in one copy of this gene lead to the production of a nonfunctional version of the RAI1 protein or reduce the amount of this protein that is produced in cells. Researchers are uncertain how changes in this protein result in the physical, mental, and behavioral problems associated with Smith-Magenis syndrome.

Related Chromosome(s)

Changes involving this chromosome are associated with Smith-Magenis syndrome.

  • chromosome 17

Related Gene(s)

Changes in this gene are associated with Smith-Magenis syndrome.

  • RAI1

Can Smith-Magenis syndrome be inherited?

Smith-Magenis syndrome is typically not inherited. This condition usually results from a genetic change that occurs during the formation of reproductive cells (eggs or sperm) or in early fetal development. Most often, people with Smith-Magenis syndrome have no history of the condition in their family.

Where can I find information about diagnosis or management of Smith-Magenis syndrome?

These resources address the diagnosis or management of Smith-Magenis syndrome and may include treatment providers.

  • Gene Review: Smith-Magenis Syndrome (
  • Genetic Testing Registry: Smith-Magenis syndrome (
  • MedlinePlus Encyclopedia: Intellectual Disability (

You might also find information on the diagnosis or management of Smith-Magenis syndrome in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about Smith-Magenis syndrome?

You may find the following resources about Smith-Magenis syndrome helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for Smith-Magenis syndrome?

  • 17p11.2 monosomy
  • 17p- syndrome
  • chromosome 17p deletion syndrome
  • deletion 17p syndrome
  • partial monosomy 17p
  • SMS

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about Smith-Magenis syndrome?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding Smith-Magenis syndrome?

anxiety ; cell ; chromosome ; contiguous ; contiguous gene deletion syndrome ; deletion ; disability ; gene ; gene deletion ; inherited ; injury ; kidney ; lower jaw ; monosomy ; mutation ; myopia ; nearsightedness ; prevalence ; protein ; reproductive cells ; scoliosis ; sensitivity ; short stature ; sperm ; stature ; syndrome ; trait

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Elsea SH, Williams SR. Smith-Magenis syndrome: haploinsufficiency of RAI1 results in altered gene regulation in neurological and metabolic pathways. Expert Rev Mol Med. 2011 Apr 19;13:e14. doi: 10.1017/S1462399411001827. Review. (
  • Gene Review: Smith-Magenis Syndrome (
  • Girirajan S, Elsas LJ 2nd, Devriendt K, Elsea SH. RAI1 variations in Smith-Magenis syndrome patients without 17p11.2 deletions. J Med Genet. 2005 Nov;42(11):820-8. Epub 2005 Mar 23. (
  • Girirajan S, Vlangos CN, Szomju BB, Edelman E, Trevors CD, Dupuis L, Nezarati M, Bunyan DJ, Elsea SH. Genotype-phenotype correlation in Smith-Magenis syndrome: evidence that multiple genes in 17p11.2 contribute to the clinical spectrum. Genet Med. 2006 Jul;8(7):417-27. (
  • Gropman AL, Duncan WC, Smith AC. Neurologic and developmental features of the Smith-Magenis syndrome (del 17p11.2). Pediatr Neurol. 2006 May;34(5):337-50. Review. (
  • Martin SC, Wolters PL, Smith AC. Adaptive and maladaptive behavior in children with Smith-Magenis Syndrome. J Autism Dev Disord. 2006 May;36(4):541-52. (
  • Shelley BP, Robertson MM. The neuropsychiatry and multisystem features of the Smith-Magenis syndrome: a review. J Neuropsychiatry Clin Neurosci. 2005 Winter;17(1):91-7. Review. (
  • Smith AC, Dykens E, Greenberg F. Behavioral phenotype of Smith-Magenis syndrome (del 17p11.2). Am J Med Genet. 1998 Mar 28;81(2):179-85. Review. (
  • Tomona N, Smith AC, Guadagnini JP, Hart TC. Craniofacial and dental phenotype of Smith-Magenis syndrome. Am J Med Genet A. 2006 Dec 1;140(23):2556-61. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: December 2013
Published: February 1, 2016