X-linked alpha-thalassemia/intellectual disability syndrome (ATR-X 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.

X-linked alpha-thalassemia/intellectual disability syndrome (ATR-X syndrome) is an X-linked genetic condition. It can occur as an inherited or de novo genetic condition, so absence of a relevant family history does not exclude the diagnosis. It occurs predominantly in males; affected females are uncommon and usually have milder or atypical manifestations. A distinctive presentation may include the combination of severe intellectual disability, characteristic facial features, genital abnormalities, with alpha-thalassemia providing an additional diagnostic clue.

It can present with psychiatric features such as emotional lability, behavioural difficulties, tantrums, and episodes of prolonged crying or laughing.

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

  • Microcephaly

  • Midface retrusion

  • Telecanthus

  • Epicanthus

  • Depressed nasal bridge

  • Short nose

  • Thick vermilion

  • Wide mouth

  • Large tongue

  • Widely spaced teeth

  • Clinodactyly of fifth fingers

Other characteristic features include hypotonia, short stature, and genital abnormalities in males such as hypospadias, undescended testes, or ambiguous genitalia. Seizures may occur. Alpha-thalassemia is usually mild. Feeding difficulties, excessive drooling, and gastrointestinal problems may also occur.

Early diagnosis is important to identify significant developmental, neurological, genital, and haematological manifestations; to support appropriate developmental and behavioural management; and to allow surveillance and management of seizures, feeding difficulties, and other medical complications.

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.