Created by Stephanie Close
EDU 1153 - Assignment 3.1 Disability Display
Angelman Syndrome
Introduction
Angelman Syndrome, also known as AS, is a rare genetic condition that can be caused by five different genetic abnormalities. All five abnormalities involve a specific area (15Q11-13) of the chromosome 15 that is inherited from the mother (See Figure 1). Because every abnormality that causes AS has to do with the mother’s chromosome 15 it is known as imprinting. Imprinting acts as an "identification tag" indicating which parent contributed the chromosome (Roggenbuck, 2012).
The most common cause (70%) of AS is a missing piece in the chromosome 15 (See Figure 2), the second most prevalent cause (11%) is gene mutation in the maternally inherited UBE3A, the third most common cause of AS (7%) comes from the inheritance of both chromosomes in the 15 pair from the father (uniparental disomy), which is a result of no contributing chromosome 15 from the mother, the fourth most common cause (3%) of AS cases involve imprinting defects on the maternally inherited chromosome 15, and lastly, the fifth common cause of AS (1%) results from the chromosome 15 being rearranged. The remaining (8%) cases of AS have unknown causes and have not been able to be linked to a genetic cause. (Roggenbuck, 2012).
In some cases of AS, individuals present with light-coloured hair and skin (when compared to family members), this occurs when the gene (called OCA2), located on the segment on chromosome 15, which is usually abnormal in individuals affected by AS, is deleted. This is the gene responsible for pigmentation of skin, hair and eyes (The U.S. National Library of Medicine, 2016). The U.S. National Library of Medicine (2016) also states that most cases of AS are not inherited, the genetic abnormalities most often occur as random events in the early stages of embryonic development.
Figure 1. The 15q11-13 region of chromosome 15 where all abnormalities resulting in AS occur.
Figure 2. The five known causes of abnormality in chromosome 15
Children with AS show delayed development, severe verbal impairment (limiting speech to a few words or no words at all), and problems with movement and balance. Children with AS most often have recurrent seizures and small head size (microcephaly). The most distinguishable and well known physical trait is a happy and excitable demeanor, jerky body movements and love for playing in water.
Watch the video below to learn more about angelman syndrome
(AngelmanSyndromeFdn, 2013)
AS is diagnosed all around the world in both male and females and all races. The exact incidence is unknown, but the prevalence of AS appears to be 1 in 15,000 (Calulator, Peters, & Williams, 2009).
AS is commonly misdiagnosed as Cerebral Palsy or Autism.
Individuals affects by AS become less excitable with age, but they continue to have mental disability, severe speech deficits and seizures all their life. The life expectancy of people with AS seems to be the same as the average population (The U.S. National Library of Medicine, 2016)