How Common Is Angelman Syndrome?

Angelman syndrome cases have been reported in different countries and among people of varying ethnic origins. The majority of cases in North America have been found in people of Caucasian descent. Over the years, there have been varying estimates of Angelman’s prevalence — or how common the disease is among the general population.

Several studies in children have attempted to find better estimates of how common Angelman is in that population. Initial estimates were around 1 in 20,000 people.

Now a new Australian study is working to update such estimates.

Prior studies to estimate Angelman syndrome prevalence

A key issue affecting estimates of how common is Angelman syndrome is how dated most of the prevalence studies are.

Researchers published a study in 1995 in which five patients received a diagnosis of Angelman syndrome over a five-year period. The children were born in Denmark during an eight-year span. During that time, 44,807 children were born in the area of Denmark that the study covered. Using those numbers, the authors estimated a prevalence of 1 in 10,000 children.

Another study in Sweden, published in 1996, examined a group of children ages 6 to 13 for Angelman syndrome. The investigators identified four children out of a population of almost 49,000. That led to a prevalence estimate of around 1 in 12,000 children.

A series of other studies have attempted to estimate prevalence in different regions of the world and over different periods of time.

One study investigated the prevalence of Angelman syndrome at a long-term care facility in the U.S. and extrapolated the data. That research, published in 1998, gave its team of scientists a prevalence rate of 1 in 20,000 people, which was similar to earlier estimates.

A Western Australia study, published in 2006, found a prevalence of 1:40,000 in people born over a 50-year period, from 1953 to 2003.

Finally, a study in Estonia, also published in 2006, found a population prevalence of 1:56,112.

Since there is such a range in estimates, the Angelman Syndrome Foundation recommends using a prevalence estimate of 1:15,000.

Factors affecting prevalence estimates

Confounding factors in these studies include their location, time span, and diagnostic method.

For example, there may be real differences in occurrence internationally.

Also, because the studies covered different time spans, they did not take into account increases or decreases in prevalence over time.

Moreover, because some studies only used clinical diagnosis without genetic diagnosis, this could falsely inflate or deflate the numbers.

Finally, the studies assessed patients who were older. Therefore, they could have potentially missed patients who died earlier before receiving a diagnosis.

Several efforts are underway to get a better estimate of how common Angelman syndrome is in current populations.

Screening efforts

A large study was announced by Australian researchers in 2018 that will involve extensive screening for a host of genetic diseases.

Some 75,000 newborn screenings will be performed in Australia for Angelman, Prader-Willi, Fragile X, and Dup15q syndromes. The study will take place at the Murdoch Children’s Research Institute in Melbourne. The Victorian Medical Research Acceleration Fund, the Angelman Syndrome Foundation (ASF), and the Foundation for Prader-Willi Research (FPWR) are sponsoring the testing and analysis.

There also are efforts underway, including in Europe, to make Angelman syndrome and other rare genetic diseases a standard part of newborn screenings. In many of these rare diseases, early diagnosis would lead to earlier treatment and improved outcomes.

Last updated: Sept. 21, 2020

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