Definition

Angelman syndrome (AS) is a genetic condition that causes severe mental retardation, severe speech impairment, and a characteristic happy and excitable demeanor.

Description

Individuals with AS show evidence of delayed development by 6–12 months of age. Eventually, this delay is recognized as severe mental retardation. Unlike some genetic conditions causing severe mental retardation, AS is

not associated with developmental regression (loss of previously attained developmental milestones).

Severe speech impairment is a striking feature of AS. Speech is almost always limited to a few words. However, receptive language skills (listening to and understanding the speech of others) and non-verbal communication are not as severely affected.

Individuals with AS have a balance disorder, causing...