Smith-Magenis syndrome (17p11.2 deletion)
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A 5-year-old presents with significant behavioral issues including self-hugging, hand-licking, and inserting objects into body orifices. Parents report severe sleep disturbance with an inverted circadian rhythm. He is friendly but has frequent outbursts.
- Deletion: 17p11.2 (~3.7 Mb common deletion)
- Critical gene: RAI1
- Can also be caused by RAI1 point variants (Smith-Magenis-like)
- Behavioral: self-hugging (stereotypic), self-injurious behaviors, outbursts
- Sleep disturbance: inverted melatonin secretion
- Brachycephaly, midface hypoplasia
- Intellectual disability (mild to moderate)
- Hoarse voice
- Chromosomal microarray detects the recurrent 17p11.2 deletion (first-line)
- If CMA is normal but the phenotype fits, RAI1 sequencing identifies point variants
- Melatonin supplementation (evening) + morning bright light therapy
- Behavioral interventions
"SMIth-MaGENis = Seventeen's MIssing GENes! (17p11.2 deletion)
MAGENIS (broader feature coverage):
- M: Midface hypoplasia
- A: Aggressive outbursts / Attention deficit
- G: Growth restriction
- E: Ear (sensorineural hearing loss)
- N: Night awakenings (inverted melatonin)
- I: Intellectual disability
- S: Self-hugging + Self-injurious behaviors