Smith-Magenis Syndrome: Symptoms and Description
Smith–Magenis syndrome is a complex neurobehavioral, developmental disorder that takes place due to mutations and interstitial deletions associated with chromosome 17p11.2 region which encodes the retinoic acid-induced 1 (RAI1) gene. Recent studies have proven that haploinsufficiency of the retinoic acid-induced 1 (RAI1) gene located on chromosome 17p11.2 is actually responsible for this disorder.
The typical symptoms of Smith-Magenis syndrome include unique facial features which progress with age, developmental delays, cognitive impairment and many behavior anomalies. Babies show feeding issues, failure to thrive, hypotonia, hyporeflexia, excessive periods of napping with need to be forcibly awakened at feeding times and general lethargy. Most patients have mild-to-moderate degrees of mental retardation.
In Smith-Magenis syndrome there are disturbed sleeping patterns, stereotypes as well as non-adaptive and self-injurious behavior patterns seen after 18 months of age and which progress into adulthood. Both kids as well as adults with Smith-Magenis syndrome show lack of attention, hyperactivity, frequent temper tantrums, attention seeking and impulsive behavior, disobedience, aggression, and self-injurious behaviors (SIB) like self-hitting, self-biting, using sharp foreign objects on body orifices (known in medical terms as polyembolokoilamania), and pulling of nails (onychotillomania).
Two very typical behaviors seen in Smith-Magenis syndrome patients are the spasmodic upper-body squeeze or "self-hug" and finger lick and page flipping ("lick and flip").