Table 1

Main clinical characteristics of AS

Consistent (100%)Frequent (more than 80%)Associated (20–80%)
Adapted from Williams CA, et al. Angelman syndrome: consensus for diagnostic criteria. Am J Med Genet 1995;56:237–8.
*Although emphasised particularly in Harry Angelman’s first description, we have not found this to be a particularly useful sign.
†The characteristic behavioural phenotype has been shown to be perhaps the most useful diagnostic marker for AS.
Severe developmental delayDelayed, disproportionate growth in head circumference, usually resulting in microcephaly by age 2Flat occiput
Speech impairment, no or minimal use of words; receptive and non-verbal communication skills higher than verbal onesSeizures, onset usually <3 years of ageOccipital groove*
Movement or balance disorder, usually ataxia of gait and/or tremulous movement of limbsCharacteristic EEG with large amplitude slow spike waves and triphasic wavesProtruding tongue
Behavioural uniqueness†: any combination of frequent laughter/smiling; apparent happy demeanor; easily excitable personality, often with hand flapping movements; hypermotoric behaviour; short attention spanTongue thrusting; suck/swallowing disorders
Feeding problems during infancy
Wide mouth, widely spaced teeth
Frequent drooling
Excessive chewing/mouthing behaviours
Hypopigmented skin, light hair and eye colour (compared to family), seen only in deletion cases
Hyperactive lower limb deep tendon reflexes
Uplifted, flexed arm position especially during ambulation
Increased sensitivity to heat
Sleep disturbance
Attraction to/fascination with water