Consensus Criteria for Diagnosis of AS
Angelman syndrome is usually not recognized in early infancy since the developmental problems are nonspecific during this time. The most common age of diagnosis is between two and five years when the characteristic behaviors and features become most evident. Parents may first suspect the diagnosis after reading about AS or meeting a child with the condition. Children with AS may have a relatively wide mouth and a protruding tongue, sometimes associated with a prominent chin (see figure). Most children with AS also appear to share the normal familial facial traits of the family and so it is unusual for them to be considered to have a “dysmorphic” facial appearance. Angelman syndrome is a distinctive clinical condition however, mainly because of its distinctive behaviors and developmental course. A summary of the developmental and physical findings has been published for the purpose of establishing clinical criteria for the diagnosis and these are listed below [1]. All of the features do not need to be present for the diagnosis to be made and the diagnosis is often first suspected when the typical behaviors are recognized.
Composite photograph of facial appearances of individuals with genetically-proven AS
Developmental and Physical Findings (from 2005 Consensus Criteria document)
Consistent (100%)
- Developmental delay, functionally severe
- Movement or balance disorder, usually ataxia of gait and/or tremulous movement of limbs. Movement disorder can be mild. May not appear as frank ataxia but can be forward lurching, unsteadiness, clumsiness, or quick, jerky motions
- Behavioral uniqueness: any combination of frequent laughter/smiling; apparent happy demeanor; easily excitable personality, often with uplifted hand-flapping or waving movements; hypermotoric behavior
- Speech impairment, none or minimal use of words; receptive and non-verbal communication skills higher than verbal ones
Frequent (more than 80%)
- Delayed, disproportionate growth in head circumference, usually resulting in microcephaly (≤2 S.D. of normal OFC) by age 2 years. Microcephaly is more pronounced in those with 15q11.2-q13 deletions.
- Seizures, onset usually < 3 yrs. of age. Seizure severity usually decreases with age but the seizure disorder lasts throughout adulthood.
- Abnormal EEG, with a characteristic pattern, as mentioned in the text. The EEG abnormalities can occur in the first 2 years of life and can precede clinical features, and are often not correlated to clinical seizure events.
Associated (20 - 80%)
- Flat occiput
- Occipital groove
- Protruding tongue
- Tongue thrusting; suck/swallowing disorders
- Feeding problems and/or truncal hypotonia during infancy
- Prognathia
- Wide mouth, wide-spaced teeth
- Frequent drooling
- Excessive chewing/mouthing behaviors
- Strabismus
- Hypopigmented skin, light hair and eye color (compared to family), seen only in deletion cases
- Hyperactive lower extremity deep tendon reflexes
- Uplifted, flexed arm position especially during ambulation
- Wide-based gait with 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 behaviors
- Obesity (in the older child)
- Scoliosis
- Constipation
1. Williams CA, Beaudet AL, Clayton-Smith J, et al., Angelman syndrome 2005: updated consensus for diagnostic criteria. Am J Med Genet A, 2006. 140(5): p. 413-8.