Smith-Magenis syndrome (or SMS) is a chromosomal disorder characterized by a recognizable pattern of physical, behavioral, and developmental features. It is caused by a missing piece of genetic material from chromosome 17, referred to as deletion 17p11.2.
Common features include: characteristic, yet subtle, facial appearance, infant feeding problems, low muscle tone, developmental delay, variable levels of intellectual disability, early speech/language delay, middle ear problems, skeletal anomalies and decreased sensitivity to pain. The syndrome also includes a distinct pattern of neurobehavioral features characterized by chronic sleep disturbances, arm hugging/hand squeezing, hyperactivity and attention problems, prolonged tantrums, sudden mood changes and/or explosive outbursts and self-injurious behaviors.
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