Table 2.

Selected Features of Alpha-thalassemia X-linked Intellectual Disability Syndrome

Feature% of Persons with FeatureComments
Developmental delay100%A minority never speak or have meaningful speech.
Intellectual disability100%Variable severity, from mild to profound
Characteristic facies
  • Hypertelorism/telecanthus
  • Small nose
  • Tented upper lip
  • Open mouth
  • Prominent lips
90%Usually present from birth, but may persist or become less distinctive in adult life. W/age, face may also coarsen w/open mouth, spaced teeth, & prominent lips.
Microcephaly75%-85%Usually present at birth; head size of those w/out microcephaly usually in lower centiles
Short stature60%-70%Usually present at birth
Gastrointestinal dysfunction70%-80%A major morbidity; incl: early feeding difficulty, vomiting, reflux, abdominal distention, obstruction, pain, & constipation
Genital anomalies70%-80%Wide range, from minimal hypospadias or undescended testes to normal-appearing female external genitalia
NeurologicHypotonia80%-90%Contributes to facial phenotype
Seizures30%-40%

From: Alpha-Thalassemia X-Linked Intellectual Disability Syndrome

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