Testing & Diagnosis for Angelman Syndrome in Children

How does a doctor know that a child has Angelman syndrome?

There are no signs of Angelman syndrome at birth. The disorder is typically diagnosed at 6 to 12 months, when parents begin to notice developmental days such as a lack of crawling or babbling. Seizures may begin at 2 to 3 years. A doctor may suspect the disorder in children who have some of these symptoms in addition to others, such as difficulty with movement and balance, a small head size with flatness in the back and frequent laughter.

To confirm a diagnosis of Angelman syndrome, your child's doctor will perform a combination of genetic tests that can include the following:

  • chromosome analysis to examine the size, shape and number of chromosomes in a cell
  • fluorescent in situ hybridization (FISH) to see if any chromosomes are missing
  • DNA methylation test to see if both copies of a gene — one from the mother and one from the father — are active
  • sequencing of the ubiquitin-protein ligase E3A (UBE3A): to look for a mutation in the maternal mutation of this gene, which is a rare cause of Angelman syndrome