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Smith-Magenis Syndrome

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Smith-Magenis Syndrome

Smith-Magenis syndrome is a rare developmental disorder, which results in mild to moderate intellectual impairment, delayed speech and language development, distinctive facial features, behavioural difficulties and sleep disturbance. It is estimated that Smith-Magenis syndrome occurs affects one in 25000 births.

Cause of Smith-Magenis Syndrome

SMS is a chromosomal disorder.  Research indicates that it is caused by the deletion of specific genetic material located on chromosome 17.  Technically, this deletion is referred to as ‘17p11.2’.  Smith Magenis Syndrome is a rare disorder.  Up until the mid 1990’s SMS was not well know and the tiny chromosomal deletion was often missed or overlooked in genetic testing.  Since that time, a specific genetic test has been developed.  Known as ‘FISH’ (Fluorescence in situ hybridisation), the test has allowed for increased accuracy in diagnosing Smith Magenis Syndrome.

Smith-Magenis syndrome does not generally run in families.  The deletion is thought to accidently occur around the time of conception (during the formation of reproductive cells or in early foetal development) – without being directly inherited from either parent.  Therefore, SMS is genetic, but not necessarily familial.

Overview of SMS Characteristics
Physical Characteristics
  • Flattened mid-face, down-turned, prominent and often rosy cheeks
  • Prominent jaw
  • Dark eyebrows that meet in the midline
  • Hypotonia (low muscle tone)
  • Oral sensory motor difficulties (reduced oral muscular strength and range of movement, difficulties with sucking and swallowing, excess saliva/drooling)
  • Middle ear infections
  • Hoarse voice , often hyponasal
  • Flat feet
  • Peripheral neuropathy
  • Short toes and fingers
  • Reduced sensitivity to pain
  • Broad gait  (walk)
Developmental and Behavioural Features
  • Overall developmental delay
  • Mild to moderate intellectual disability
  • Sensory integration difficulties
  • Speech and language delay
  • Teeth grinding and mouthing objects and hands (beyond what is typically seen in development)
  • Difficulty toilet training
  • Sleep disturbances
  • Tendancy for self injurious behaviours.  These may include head banging, biting, picking at skin, and pulling off finger and toenails (older ages)
  • Higher executive function deficits including; hyperactivity, impulsivity, attention seeking, mood shifts, outbursts and prolonged tantrums.
Other Features
  • Hearing impairment
  • Scholiosis
  • Strabismus

(See this link for further details: prisms)

Treatment and Therapy

The provision of early intervention services can assist people with Smith-Magenis syndrome to reach their full potential. Each treatment plan will be tailored to the specific needs of each child, but more often than not, therapy will include aspects of:

  • School based learning support
  • Speech and language therapy
  • Occupational therapy and/or physiotherapy

An early intervention support team can support a child’s development. As part of our services at ENT Clinic Randwick, we are able to provide early intervention speech pathology services to children with Smith-Magenis syndrome and support to their families.  Speech pathology programs support communication development and feeding and swallowing difficulties.

Better Start

We are approved providers of the Australian government’s Better Start program which provides financial support for children (under the age of 6) if they are deemed eligible (in this instance, a confirmed diagnosis of Smith-Magenis Syndrome). If you would like further information about how our speech pathology team can support your child, please call 1300 123 368.

Contact us for results focused speech therapy

This article was written by our speech pathologist Jenna Butterworth who is a Speech Pathology Australia member.

If you have questions about Smith-Magenis Syndrome, speech pathology or for results focused speech therapy, contact your local doctor who will arrange for you to see a speech pathologist in Sydney. Contact us today!

Additional Resources:

PRISM Parents and Researchers Interested in Smith-Magenis
Gene Review Smith-Magenis Syndrome

Bibliography

Elsea, S.H. & Girirajan, S. (2008).  Smith-Magenis Syndrome. European Journal of Human Genetics, 16, 412-421.

Genetic and Rare Diseases Information Centre (2012). Smith-Magenis Syndrome.  Retrieved on 14/08/13 from National Institute of Health.

Smith, A.C.M et al. (2012). Smith-Magenis Syndrome – Genetic Counseling. GeneReviews. Retrieved on 14/08/2013 from  NCBI

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