Angelman syndrome signs and symptoms include:

• Developmental delays, including no crawling or babbling at 6 to 12 months
• Intellectual disability
• No speech or minimal speech
• Difficulty walking, moving or balancing well (ataxia)
• Frequent smiling and laughter
• Happy, excitable personality

People who have Angelman syndrome may also have other signs and symptoms, including:

• Seizures, usually beginning between 2 and 3 years of age
• Stiff or jerky movements
• Small head size, with flatness in the back of the head (microbrachycephaly)
• Tongue thrusting
• Hair, skin and eyes that are light in color (hypopigmentation)
• Unusual behaviors, such as hand flapping and arms uplifted while walking

Angelman syndrome is a genetic disorder. It's usually caused by problems with a gene located on chromosome 15 called the ubiquitin protein ligase E3A (UBE3A) gene.

A missing or defective gene

You receive your pairs of genes from your parents — one copy from your mother (maternal copy) and the other from your father (paternal copy).

Your cells typically use information from both copies, but in a small number of genes, only one copy is active.

Normally, only the maternal copy of the UBE3A gene is active in the brain. Most cases of Angelman syndrome occur when part of the maternal copy is missing or damaged.

In a few cases, Angelman syndrome is caused when two paternal copies of the gene are inherited, instead of one from each parent.

Angelman syndrome is rare. Researchers usually don't know what causes the genetic changes that result in Angelman syndrome. Most people with Angelman syndrome don't have a family history of the disease.

Occasionally, Angelman syndrome may be inherited from a parent. A family history of the disease may increase a baby's risk of developing Angelman syndrome.

Complications associated with Angelman syndrome include:

• Feeding difficulties. Difficulty coordinating sucking and swallowing may cause feeding problems in infants. Your pediatrician may recommend a high-calorie formula to help your baby gain weight.
• Hyperactivity. Children with Angelman syndrome often move quickly from one activity to another, have a short attention span, and keep their hands or a toy in their mouths. Hyperactivity often decreases with age, and medication usually isn't necessary.
• Sleep disorders. People with Angelman syndrome often have abnormal sleep-wake patterns and need less sleep than most people. Sleep difficulties may improve with age. Medication and behavior therapy may help control sleep disorders.
• Curving of the spine (scoliosis). Some people with Angelman syndrome develop an abnormal side-to-side spinal curvature over time.
• Obesity. Older children with Angelman syndrome tend to have large appetites, which may lead to obesity.