Findings typically present in affected individuals
- Normal prenatal and birth history, normal head circumference at birth, no major birth defects.
- Normal metabolic, hematologic, and chemical laboratory profiles.
- Structurally normal brain by magnetic resonance imaging (MRI) or computed tomography, although mild cortical atrophy or dysmyelination may be observed.
- Delayed attainment of developmental milestones without loss of skills.
- Evidence of developmental delay by age 6 to 12 months, eventually classified as severe.
- Speech impairment, with minimal to no use of words; receptive language skills and nonverbal communication skills higher than expressive language skills.
- Movement or balance disorder, usually ataxia of gait and/or tremulous movement of the limbs.
- Behavioural uniqueness, including any combination of frequent laughter/smiling; apparent happy demeanour; excitability, often with hand-flapping movements; hypermotoric behavior; short attention span.
Findings in more than 80% of affected individuals
- Delayed or disproportionately slow growth in head circumference, usually resulting in absolute or relative microcephaly by age 2 years.
- Seizures, usually starting before age 3 years.
- Abnormal electroencephalogram (EEG), with a characteristic pattern of large-amplitude slow-spike waves.
Findings in fewer than 80% of affected individuals
- Flat occiput.
- Occipital groove.
- Protruding tongue.
- Tongue thrusting; suck/swallowing disorders.
- Feeding problems and/or muscle hypotonia during infancy.
- Wide mouth, wide-spaced teeth.
- Frequent drooling.
- Excessive chewing/mouthing behaviours.
- Hypopigmented skin, light hair and eye color (compared with family); seen only in those with a deletion.
- Hyperactive lower-extremity deep-tendon reflexes.
- Uplifted, flexed arm position especially during ambulation.
- Wide-based gait with out-going (i.e., pronated or valgus-positioned) ankles.
- Increased sensitivity to heat.
- Abnormal sleep-wake cycles and diminished need for sleep.
- Attraction to/fascination with water; fascination with crinkly items such as certain papers and plastics.
- Abnormal food-related behaviours.
- Obesity (in the older child; more common in those who do not have a deletion).
From: “Genetics in Medicine:”Clinical and genetic aspects of Angelman Syndrome.” Charles A Williams, MD, Daniel J Driscoll, PhD, MD and Aditi I. Dagli MD. May 2010 © 2010 Lippincott Williams & Wilkins