Smith-Magenis Syndrome

Smith-Magenis Syndrome

Description, Causes and Risk Factors:

Abbreviation: SMS.

Smith-Magenis syndrome (SMS) is a complex neurobehavioral disorder caused by haploinsufficiency of the retinoic acid-induced 1 (RAI1) gene on chromosome 17p11.2, with a prevalence estimated at 1/25000. Patients with SMS have a distinctive somatic and behavioral phenotype that has been extensively studied.

All patients with SMS show sleep disorders with early sleep onset, difficulty in falling asleep, difficulty in staying asleep, frequent awakening, early waking, reduced rapid eye movement (REM) sleep, and decreased sleep time. These children go to bed early, have frequent arousals during the night, and wake up early in the morning. During the daytime they feel tired in the morning, have frequent naps, and then have heavy drowsiness in the evening.


SMS is associated with a specific pattern ofphysical, developmental, and behavioralfeatures, including:

    Sleep disturbance.

  • Intellectual disabilities.

  • Characteristic facial appearance.

  • Hearing and vision problems.

  • Speech difficulties.

  • Attention-seeking behavior.

  • Self-injurious behaviors, particularlyhead-banging; skin and nail picking.

  • Prolonged tantrums.

  • Property destruction.

  • Aggression.


Diagnostic strategies include molecularidentification of a 17p11.2 microdeletion encompassing RAI1 or a mutation in RAI1. G-banding andfluorescent in situ hybridization (FISH) are the classical methods used to detect the SMS deletions, whilemultiplex ligation-dependent probe amplification (MLPA) and real-time quantitative PCR are the newer,cost-effective, and high-throughput technologies.


Treatment for Smith-Magenis syndrome relies on managing its symptoms. Children with SMS often require several forms of support, including physical therapy, occupational therapy and speech therapy. Support is often required throughout an affected person's lifetime.

Medication is often used to address some symptoms. Melatonin supplements and trazodone are commonly used to regulate sleep disturbances. Other medications such as risperdal are sometimes used to regulate violent behavior.

Medication risks and benefits must be discussed with the consulting physician.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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