Diagnosis

Your child's doctor may suspect Angelman syndrome if your child has developmental delays and other signs and symptoms of the disorder, such as problems with movement and balance, a small head size, flatness in the back of the head, and frequent laughter.

Tests

A definitive diagnosis can almost always be made through a blood test. This genetic testing can identify abnormalities in your child's chromosomes that indicate Angelman syndrome.

A combination of genetic tests can reveal the chromosome defects related to Angelman syndrome. These tests may review:

• Parental DNA pattern. This test, known as a DNA methylation test, screens for three of the four known genetic abnormalities that cause Angelman syndrome.
• Missing chromosomes. A chromosomal microarray (CMA) can show if portions of chromosomes are missing.
• Gene mutation. Rarely, Angelman syndrome may occur when a person's maternal copy of the UBE3A gene is active, but mutated. If results from a DNA methylation test are normal, your child's doctor may order a UBE3A gene sequencing test to look for a maternal mutation.