This site is intended for healthcare professionals

Go to /sign-in page

You can view 5 more pages before signing in

Smith - Magenis syndrome

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Smith-Magenis syndrome (SMS) Smith-Magenis syndrome is a rare, complex multisystemic disorder featuring, mental retardation and multiple congenital anomalies caused by a heterozygous interstitial deletion of chromosome 17p11.2

  • phenotype of Smith-Magenis syndrome is characterized by a distinct pattern of features including infantile hypotonia, generalized complacency and lethargy in infancy, minor skeletal (brachycephaly, brachydactyly) and craniofacial features, ocular abnormalities, middle ear and laryngeal abnormalities including hoarse voice, as well as marked early expressive speech and language delays, psychomotor and growth retardation, and a 24-hour sleep disturbance
    • majority of individuals function in the mild-to-moderate range of intellectual disability

  • infants have feeding difficulties, failure to thrive, hypotonia, hyporeflexia, prolonged napping or need to be awakened for feeds, and generalized lethargy

    • the behavioural features (including significant sleep disturbance, stereotypies, and maladaptive and self-injurious behaviors) - are not generally not recognized until age 18 months or older and continues to change until adulthood
    • sensory issues are frequently noted
      • include avoidant behavior, as well as repetitive seeking of textures, sounds, and experiences
    • toileting difficulties are common
    • significant anxiety is common
    • problems with executive functioning also are common - including inattention, distractibility, hyperactivity, and impulsivity
    • maladaptive behaviors include:
      • frequent outbursts / temper tantrums,
      • attention-seeking behaviors,
      • opposition, aggression, and
      • self-injurious behaviors
        • including self-hitting, self-biting, skin picking, inserting foreign objects into body orifices (polyembolokoilamania), and yanking fingernails and/or toenails (onychotillomania)
      • spasmodic upper-body squeeze or "self-hug" seems to be highly associated with SMS

Diagnosis:

  • established in a proband who has suggestive clinical findings and either a heterozygous deletion at chromosome 17p11.2 that includes RAI1 or a heterozygous intragenic RAI1 pathogenic variant.

Reference:

Pediatr Neurol. 2006 May;34(5):337-50.


Create an account to add page annotations

Annotations allow you to add information to this page that would be handy to have on hand during a consultation. E.g. a website or number. This information will always show when you visit this page.

The content herein is provided for informational purposes and does not replace the need to apply professional clinical judgement when diagnosing or treating any medical condition. A licensed medical practitioner should be consulted for diagnosis and treatment of any and all medical conditions.

Connect

Copyright 2024 Oxbridge Solutions Limited, a subsidiary of OmniaMed Communications Limited. All rights reserved. Any distribution or duplication of the information contained herein is strictly prohibited. Oxbridge Solutions receives funding from advertising but maintains editorial independence.