The prevalence of Angelman Syndrome (AS) is one in 12,000-20,000. AS is characterized by: 1) severe developmental
delay or mental retardation; 2) severe speech impairment; 3) gait ataxia and/or tremulousness of the limbs; and 4) a unique
behavior with an inappropriate happy demeanor that includes frequent laughing, smiling, and excitability. In addition,
microcephaly (small head) and seizures are common.
The average child with AS walks between two and one-half and six years of age and at that time may have a jerky, robot-like,
stiff gait, with uplifted, flexed, and pronated forearms, hypermotoric activity, excessive laughter, protruding tongue, drooling,
absent speech, and social-seeking behavior. Ten percent of children are non-ambulatory. Sleep disorders are common.
Essentially all young children with AS have some component of hyperactivity. Infants and toddlers may have seemingly
ceaseless activity, constantly keeping their hands or toys in their mouth, moving from object to object. Parents report
that decreased need for sleep and abnormal sleep/wake cycles are characteristic of AS.
Short attention span is present in most. Language impairment is severe. Appropriate use of even one or two
words in a consistent manner is rare. Receptive language skills are always more advanced than expressive language skills.
Most older children and adults with AS are able to communicate by pointing and using gestures and by using communication boards.
Effective fluent use of sign language does not occur.
Young adults appear to have good physical health with the exception of possible seizures. Independent living is
not possible for adults with AS, but most can live at home or in home-like placements. Life span appears to be nearly
normal.
