Traits & Symptoms

Many of the typical characteristics of Angleman syndrome (AS) are not evident at birth. However, some individuals with AS may have nursing and feeding difficulties starting in infancy. More noticeable delays in development are usually evident around 6-12 months of age. It is important to note that Angelman syndrome is a spectrum disorder, so not all individuals exhibit the same behavioral characteristics or preferences.

Findings typically present in individuals with AS:

• Normal prenatal and birth history, normal head circumference at birth, no major birth defects.

• Normal metabolic, hematologic, and chemical laboratory profiles.

• Structurally normal brain by magnetic resonance imaging (MRI) or computed tomography, although mild cortical atrophy or dysmyelination may be observed.

• Delayed attainment of developmental milestones without regression (loss of skills) by 6-12 months.

• Severe speech impairment, with minimal to no use of words; receptive language skills (ex: following directions) and nonverbal communication skills (ex: using gestures) are often higher than expressive language skills.

• Movement or balance disorder, usually ataxia of gait and/or tremulous movement of the limbs.

• Behavioral uniqueness, including any combination of frequent laughter/smiling; apparent happy demeanor; excitability, often with hand-flapping movements; hypermotoric behavior; short attention span.

Additional common findings:

• Delayed or disproportionately slow growth in head circumference

• Abnormal electroencephalogram (EEG), with a characteristic pattern of large-amplitude slow-spike waves.

• Seizures, usually starting before age 3

• Suck/swallowing disorders

• Muscle hypotonia during infancy

• Excessive chewing/mouthing behaviors, including non-edible objects

• Strabismus

• Hypopigmented skin, light hair and eye color (compared with family); seen only in those with a deletion.

• Hyperactive lower-extremity deep-tendon reflexes

• Wide-based gait with out-going ankles

• Abnormal sleep-wake cycles and disrupted sleep

• Attraction to/fascination with water

• Scoliosis

• Constipation