Diagnostic Criteria for
Angelman Syndrome

• Developmental delay, functionally severe (100%)
• Speech impairment, none or minimal use of words; receptive and nonverbal communication skills higher than verbal ones (100%)
• Movement or balance disorder, usually ataxia of gait and/or tremulous
movement of limbs (100%)
• Behavioral uniqueness: any combination of frequent laughter/smiling;
apparent happy demeanor; easily excitable personality, often with hand
fl apping movements; hypermotoric behavior; short attention span (100%)
• Delayed, disproportionate growth in head circumference, usually resulting in microcephaly (absolute or relative) by age 2 (80%)
• Seizures, onset usually <3 years of age (80%)
• Abnormal EEG, characteristic pattern with large amplitude slow-spike
waves (usually 2-3/s), facilitated by eye closure (80%)
• Flat occiput (20-80%)
• Occipital groove (20-80%)
• Protruding tongue (20-80%)
• Tongue thrusting; suck/swallowing disorders (20-80%)
• Feeding problems during infancy (20-80%)
• Prognathia (20-80%)
• Wide mouth, wide-spaced teeth (20-80%)
• Frequent drooling (20-80%)
• Excessive chewing/mouthing behaviors (20-80%)
• Strabismus (20-80%)
• Hypopigmented skin, light hair and eye color (compared to family), seen only in deletion cases (20-80%)
• Hyperactive lower limb deep tendon refl exes (20-80%)
• Uplifted, fl exed arm position especially during ambulation (20-80%)
• Increased sensitivity to heat (20-80%)
• Sleep disturbance (20-80%)
• Attraction to/fascination with water (20-80%)

From: “Angelman syndrome 2005: updated consensus for diagnostic criteria.” Williams CA
et al, Am J Med Genet A. 2006 Mar 1;140(5):413-8. PMID: 16470747