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Angelman Syndrome Chromosome

Angelman syndrome is a complex genetic disorder that primarily affects the nervous system. Typical features of this condition include delayed development, intellectual disability, severe speech impairment, and problems with movement and balance (ataxia). Most affected children also have frequent seizures (epilepsy) and a small head (microcephaly). Delayed development becomes noticeable by 6 to 12 months of age, and other common signs and symptoms usually appear throughout childhood.

Children with Angelman syndrome usually have happy, enthusiastic behavior, including frequent smiling, laughing, and hand waving. Hyperactivity and poor attention span are common. Most affected children also have difficulty sleeping and require less sleep than usual.

Angelman syndrome is a genetic condition that is present at birth (congenital). Most cases occur when a certain gene (the UBE3A gene) on chromosome 15 is missing (deleted).

Reason

Many of the characteristic features of Angelman syndrome result from the loss of function of a gene called UBE3A. People usually inherit one copy of the UBE3A gene from each parent. Both copies of this gene are active (active) in most tissues of the body. However, in nerve cells (neurons) in the brain and spinal cord (central nervous system), only the copy inherited from a person’s mother (the maternal copy) is active. This parent-specific gene activation occurs due to a phenomenon called genomic imprinting. If the maternal copy of the UBE3A gene is lost due to a chromosomal change or gene variant (also known as a mutation), the person will have no active copy of the gene in most parts of the brain.