Testing and Diagnosis of Angelman Syndrome

Testing and Diagnosis

Due to common characteristics that AS shares with other disorders (developmental delays, motor issues, and lack of cooing, babbling or speech), 50% of individuals with Angelman syndrome are originally misdiagnosed. Late or misdiagnosis may cause individuals to lose opportunities for early intervention programs, resources, personalized support or life-changing treatments.

Testing and diagnosis of AS is done through a medical doctor.  To find a clinician in your area to perform genetic testing, see the Genetic Testing Registry or contact the ASF.

Genetic Testing

Below are the tests that help determine whether AS is present.  All of these tests are done through a blood test and the final results of genetic testing can take a couple weeks or more.

methylation test can identify whether the UBE3A gene is functioning properly.  If the methylation test determines that UBE3A is abnormal, that means the person has AS and the next step is to determine the genetic type.

If the methylation test is normal, DNA sequencing of the UBE3A gene is performed to confirm whether the UBE3A gene is functional. In this case it is likely that the patient has a condition that mimics AS.

FISH 15 test (fluorescent in situ hybridization) or comparative genomic hybridization (CGH) test will find chromosome deletion (or deletion positive), which is 70% of all individuals with AS.  If the FISH 15/CHG test is normal, then the person is not deletion positive.

DNA Marker Analysis  will determine whether the type of AS is Paternal uniparental disomy (UPD).  If the type is not UPD, then an Imprinting Center Defect is assumed, but molecular study of the imprinting center can confirm.

See the diagram below that summarizes the test sequencing.

Diagnostic Testing for AS

See more about the different genetic mechanisms of AS.


After receiving a diagnosis of Angelman syndrome, many parents are overwhelmed by the fact that they know nothing about the syndrome and the road ahead.

The good news is that we know that an individual with AS is able to do and accomplish more than was believed years ago. Parents were told their child would never walk and never communicate.  We know now, that is not true. People with AS today are walking, communicating and graduating high school.

Early intervention is key. Talk to your child’s doctor about potential therapies to help with development.  Will there be some rough road ahead? Probably. But the Angelman Syndrome Foundation is here to help as well as a community of families, caregivers, therapists, researchers and physicians from all over the world.

If your child was recently diagnosed with Angelman syndrome, see the Newly Diagnosed page and fill out the form today.