Tests and diagnosis

By Mayo Clinic Staff

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, small head size, and flatness in the back of the head, along with frequent laughter.

Confirming a diagnosis of Angelman syndrome requires taking a blood sample from your child for genetic studies. A combination of genetic tests can reveal the chromosome defects related to Angelman syndrome. These tests may look at:

  • Chromosome size, shape and number. This test, known as chromosome analysis (karyotyping), examines chromosomes in a cell sample.
  • Missing chromosomes. Known as fluorescence in situ hybridization (FISH), this test can show if portions of any chromosomes are missing.
  • Parental DNA pattern. This test, known as a DNA methylation test, reveals a gene's imprinting pattern. Normal results show both a paternal and maternal DNA pattern — meaning genes from both parents are active. In some areas of the brain, only the maternal gene is active. In most cases for people with Angelman syndrome, the maternal copy of the gene is lost, so there are no copies of the gene operating in the brain.
  • 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.
Jan. 17, 2012