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About Angelman Syndrome

Testing & Diagnosis

For decades, including during and after the moment that Dr. Harry Angelman first identified the disorder in 1965, all people with AS had only “clinical” diagnoses—a determination based not on their genetic material, but on traits and symptoms.

These days, there isn’t one definitive test for AS, but rather—and this is good news!—numerous tests. If you are trying to understand the test results of your child or someone else, it is important to know exactly which test(s) the child has had. It is common for parents to know their child was tested for AS and to remember the geneticist telling them the test was either positive or negative, but different genetic errors can cause AS—which means different tests are needed to detect them.

Additionally, about one in ten individuals who have all the key symptoms of Angelman syndrome have normal or “negative” results on all these tests. These individuals may receive a “clinical” diagnosis of AS. This means the individual meets the diagnostic criteria of AS but we don’t know what kind of genetic error is causing their symptoms.

In the early 1990s, the first tests were developed to test Chromosome 15 for deletions. But scientific progress can sometimes inadvertently lead to confusion, as people understandably assume—especially when it comes to genetics—that there is a straight path to a clear and conclusive answer.

Further research into the genetics of Angelman syndrome is likely to yield more causes of AS and, therefore, more tests to confirm the clinical diagnosis. For now, the ones available are:

Standard Chromosome Analysis or Cytogenetics Analysis

The DNA Methylation Test

The FISH Test

PCR Assay

UBE3A Sequencing

There is greater detail about these tests here.

If you need help understanding or planning your own tests, write to us at

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