Smith-Magenis syndrome (17p11.2 microdeletion syndrome)

Page most recently updated 7 September 2026

This page focuses on the reported psychiatric associations, which may be the initial presenting manifestation, and on other clinical features that may assist the psychiatrist or primary care physician in identifying the underlying diagnosis, considered through the lenses of the diagnostic lenses framework.

Smith-Magenis syndrome (17p11.2 microdeletion syndrome) is a rare genetic condition. It is an autosomal dominant genetic condition, although most cases occur as a de novo genetic condition; therefore, absence of a relevant family history does not exclude the diagnosis. A distinctive presentation may include the combination of flat facies, flat occiput, brachydactyly, speech delay, an inverted sleep-wake rhythm, and self-injurious behaviours.

It can present with psychiatric features such as ADHD, anxiety, autism spectrum disorder (ASD), behavioural dysregulation, impulsivity, aggression, stereotypic behaviours, self-injurious behaviour, attention-seeking behaviours and sleep disturbance. Behavioural manifestations can be particularly distinctive, including stereotypic behaviours such as the characteristic “self-hug” behaviour, attention-seeking behaviours, aggression and impulsivity, as well as self-injurious behaviours including self-hitting, skin picking, onychotillomania (compulsive nail pulling) and insertion of foreign objects into body orifices. Severe sleep disturbance with an inverted circadian rhythm is characteristic and may contribute substantially to daytime behavioural difficulties. Other reported psychiatric manifestations include mood symptoms and psychotic symptoms, although these are not characteristic of the syndrome. Behavioural and sleep manifestations generally emerge during childhood and may become more prominent or change with age; psychiatric and behavioural difficulties can persist into adulthood.

From a morphologic lens perspective, other features include (but are not limited to):

  • Flat occiput

  • Prominent forehead

  • Flat face

  • Prognathism

  • Synophrys

  • Low-set ears

  • Broad nasal bridge

  • Brachydactyly

Other characteristic features include infantile hypotonia and developmental delay, with most affected individuals having mild to moderate intellectual disability and prominent speech and language impairment. Other features include short stature, childhood-onset obesity with disproportionate abdominal fat accumulation, scoliosis, hearing loss and hyperacusis, ocular abnormalities, dental abnormalities, chronic constipation and, less commonly, cardiac, renal and urinary tract abnormalities. The characteristic facial appearance may become more distinctive with age. Seizures occur in a minority of affected individuals.

Early diagnosis is important to identify and manage the characteristic behavioural and sleep disturbances; recognise associated developmental, neurological and medical complications; assess hearing, vision and other associated medical complications; provide appropriate developmental, educational and psychiatric assessment and support; and facilitate genetic counselling and recurrence-risk assessment for the family.

Selected references and further reading — Morphologic lens

Jones KL, Jones MC, del Campo M. Smith's recognizable patterns of human malformation. 8th ed. Philadelphia: Elsevier; 2021.

Reardon W. The bedside dysmorphologist: a guide to identifying and assessing congenital malformations. 2nd ed. Oxford: Oxford University Press; 2016.

Allanson JE, Biesecker LG, Carey JC, Hennekam RCM. Elements of morphology: introduction. Am J Med Genet A. 2009;149A(1):2-5. doi:10.1002/ajmg.a.32601.

Hennekam RCM, Biesecker LG, Allanson JE, Hall JG, Opitz JM, Temple IK, Carey JC; Elements of Morphology Consortium. Elements of morphology: general terms for congenital anomalies. Am J Med Genet A. 2013;161A(11):2726-2733. doi:10.1002/ajmg.a.36249.