GTR Home > Conditions/Phenotypes > Smith-Magenis syndrome


Excerpted from the GeneReview: Smith-Magenis Syndrome
Smith-Magenis syndrome (SMS) is characterized by distinctive physical features (particularly facial features that progress with age), developmental delay, cognitive impairment, and behavioral abnormalities. Infants have feeding difficulties, failure to thrive, hypotonia, hyporeflexia, prolonged napping or need to be awakened for feeds, and generalized lethargy. The majority of individuals function in the mild-to-moderate range of intellectual disability. The behavioral phenotype, including significant sleep disturbance, stereotypies, and maladaptive and self-injurious behaviors, is generally not recognized until age 18 months or older and continues to change until adulthood. Sensory integration issues are frequently noted. Children and adults typically have inattention, distractibility, hyperactivity, impulsivity, maladaptive behaviors including frequent outbursts/temper tantrums, attention seeking, disobedience, aggression, toileting difficulties, and self-injurious behaviors (SIB) including self-hitting, self-biting, and/or skin picking, inserting foreign objects into body orifices (polyembolokoilamania), and yanking fingernails and/or toenails (onychotillomania). Among the stereotypic behaviors described, the spasmodic upper-body squeeze or "self-hug" seems to be highly associated with SMS. The finger lick and page flipping ("lick and flip") behavior may be less prevalent than initially reported. An underlying developmental asynchrony, specifically between intellectual functioning and emotional maturity, may also contribute to maladaptive behaviors in people with SMS.

Genes See tests for all associated and related genes

  • Also known as: SMCR, SMS, RAI1
    Summary: retinoic acid induced 1

Practice guidelines

  • ACMG, 2013
    Clinical genetics evaluation in identifying the etiology of autism spectrum disorders: 2013 guideline revisions.

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