Sienna's Steps

What is Smith-Magenis Syndrome?

Smith-Magenis Syndrome (SMS) is a non-familial chromosomal disorder characterized by a recognizable pattern of physical, behavorial, and developmental features. It is the result of a small missing piece of genetic material in chromosome 17, known as a microdeletion, and referred to as deletion 17p11.2. Smith-Magenis Syndrome is quite rare, occurring in approximately 1 in 25,000 births.

Common Features of individuals with SMS

  • Sleep disturbances, daytime sleepiness
  • Low muscle tone
  • Feeding problems as infants
  • Developmental Delays
  • Varying degrees of cognitive impairment
  • Early speech delays
  • Middle ear problems
  • Scoliosis
  • Skeletal anomolies
  • Decreased sensitivity to pain

Common Neurobehavioral Features

  • Endearing, loving personalities 
  • Self Injurious Behavior
  • Hyperactivity/ADD
  • Arm hugging/hand squeezing
  • Prolonged tantrums
  • Sudden mood changes and/or explosive outbursts

For more information about SMS, please visit