Angelman syndrome (AS) is a rare neurogenetic disorder that affects approximately one in 15,000 people – about 500,000 individuals worldwide. Children and adults with AS typically have impaired motor and balance, and debilitating seizures. Some individuals never walk. The majority do not speak. Disrupted sleep cycles also can be a serious challenge to the individual and caregivers. Individuals with AS require continuous care and are unable to live independently. They have a normal life expectancy. People with Angelman syndrome have some distinct behavioural traits, including a happy demeanour, characterised by frequent laughing, smiling and excitability. Many individuals with AS have a fascination with water and take great pleasure in activities like swimming.
What causes it?
Angelman syndrome (AS) is a single-gene disorder caused by a loss of function in the UBE3A gene on the maternal 15th chromosome. People have two sets of chromosomes – one inherited from the mother and one from the father. In a typical person, the maternally inherited UBE3A gene is active, while the copy of the gene inherited from the father is silenced in the neurons in our brains – a phenomenon known as imprinting. For people with AS, this maternal gene is not doing its job.
How are individuals tested?
While a single test can confirm Angelman syndrome, one negative test result does not rule it out. DNA microarray testing has made it easier to test for Angelman syndrome. Microarray will detect a microdeletion at chromosome 15, the most common cause, however, approximately 25% of cases will require further testing to confirm or exclude a diagnosis of AS. If you suspect your loved one has AS, your doctor or paediatrician can refer you to a specialist, such as a paediatrician, neurologist or geneticist, for assessment and testing.