People with Angelman syndrome (AS) have an unusual facial appearance, short stature, severe mental retardation with a lack of speech, stiff arm movements, and a spastic, uncoordinated walk. They may have seizures and often have inappropriate outbursts of laughter.
Angelman syndrome can result when a baby inherits both copies of a section of chromosome #15 from the father (rather than one from the mother and one from the father). AS can also occur even when chromosome #15 is inherited normally—one chromosome coming from each parent. If that section of the mother's chromosome #15 is deleted, only the father's section will be present, allowing AS symptoms to occur. This situation occurs in about 5 percent of AS and is called paternal uniparental disomy.