Angelman syndrome is best known as a complex genetic disorder. It primarily affects the nervous system. This disorder is characterized by delayed development (in children), severe speech impediments, intellectual disabilities and problems with movement and balance. Many of these signs and symptoms usually develop during early childhood, sometimes as early as 6 months.
Stats About Angelman Syndrome
Statistics about the development of Angelman syndrome state that:
1. Most cases of Angelman syndrome, about 70 percent, occur when a segment of the maternal chromosome 15 that contains that gene gets deleted.
2. Other cases, about 11 percent, result in Angelman syndrome after a mutation in the maternal copy of Ubiquitin-protein ligase E3A occurs.
Smaller percentages of cases report that Angelman syndrome may occur when a person inherits two copies of chromosome 15 from their father (paternal copies) instead of one copy from each parent (paternal and maternal copies), an instance known as paternal uniparental disomy.
Rarer cases report Angelman syndrome developing from a chromosomal arrangement known as a translocation, a mutation or other type of defect occurring in the DNA region controlling the Ubiquitin-protein ligase E3A gene. In those cases, the genetic changes that occur abnormally turn off or inactivate the Ubiquitin-protein ligase E3A gene (or other genes) within the maternal chromosome 15.
Many causes of Angelman syndrome are actually unknown in as much as 10 to 15 percent of affected people. In those cases, the cause of the disorder is attributed to other changes in different genes or chromosomes.
Additional Statistics
Angelman syndrome is actually relatively under-researched, though statistics exist to show how many people actually experience the disorder.
Although Angelman syndrome is a genetic disorder, 70 to 75 percent of individuals born with the condition have no family history of the disorder. Even though that many people are born with Angelman syndrome each year, data regarding the conditions show that it only affects an estimated 1 in 12,000 (to 20,000) people.
The aforementioned results were taken from a study conducted in Sweden and Denmark with school age children (6 to 13 years). Data also originates from a study conducted in Denmark at medical clinics where Angelman syndrome children were born.
The Danish study showed that there was a 1 in 10,000 prevalence of Angelman syndrome. The Swedish study, in comparison, found a 1 in 12,000 prevalence of Angelman syndrome.
Studies with data regarding the prevalence of Angelman syndrome among those with developmental delay showed rates of 0 percent, 1.3 percent, 1.4 percent and 4.8 percent. That data was taken from several reports attempting to find out and address the prevalence of Angelman syndrome among those with established developmental delay.
Other than the data from the aforementioned reports, there’s a lack of extensive data showing more up-to-date statistics about Angelman syndrome. What does exist, however, gives parents and medical care providers more information about how to treat and manage Angelman syndrome in children and adults.
About Angelman Syndrome
As mentioned, Angelman syndrome primarily affects the nervous system. The condition mainly manifests in young children, typically in those around 6 to 12 months old, when delayed development might become noticeable.
Children who have Angelman syndrome commonly exhibit excitable behavior, such as frequent laughter, smiling and hand-flapping movements. Hyperactivity and shorter attention spans are common, in addition to having a distinct fascination with water. Most children affected with Angelman syndrome need less sleep than most children. They’re also known to have difficulties sleeping, as well.
When people with Angelman syndrome age, they do become less excitable and experience less sleeping problems. They do, however, continue to experience the intellectual disabilities, seizures and severe speech impediment associated with the condition. Despite that, people with Angelman syndrome do have a normal life expectancy.
Adults who have Angelman syndrome possess distinct (coarse) facial features; they also have ‘unusually fair skin and hair’ and an abnormal ‘side to side’ spinal curvature, also known as scoliosis.
Genetics and Angelman syndrome
Angelman syndrome is a genetic disorder. Many of the physical and mental changes resulting from Angelman syndrome originate from the loss of the UBE3A (Ubiquitin-protein ligase E3A) gene function.
People typically inherit one copy of Ubiquitin-protein ligase E3A from each parent. Both copies remain active (from inheritance) in much of the body’s tissues. In certain areas of the brain, the copy inherited from the mother (the maternal copy) is active. This specific gene activation is caused by something known as genomic imprinting.
If there’s no maternal copy of Ubiquitin-protein ligase E3A in the brain, a person won’t have any active copies of Ubiquitin-protein ligase E3A within some parts of the brain. In most cases, the maternal copy of Ubiquitin-protein ligase E3A is lost through genetic mutations or chromosomal changes. Many mechanisms of genetics can outright delete or inactivate the maternal copy of Ubiquitin-protein ligase E3A, causing the resultant child to develop Angelman syndrome.