Angelman syndrome
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Angelman syndrome (AS) is neurological disorder in which severe learning difficulties are associated with a characteristic facial appearance and behavior.
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History
Dr. Harry Angelman, a pediatrician working in Warrington, Cheshire, first reported three children with this condition in 1965. It was initially presumed to be rare. In 1987, it was first noted that around half of the children with AS have a small piece of chromosome 15 missing (chromosome 15q partial deletion). Since this time the condition has been reported more frequently and the incidence is now thought to be 1 in 25,000 children.
Pathophysiology
AS is due to abnormal expression of a group of genes on chromosome 15. It is likely that at least one of these genes controls development of the brain, especially the parts associated with language, movement and pigmentation. It seems also that some genes influence chemical transmission of messages within the brain.
The gene of Angelman syndrome (part of the ubiquitin pathway) is expressed only on the maternal chromosome. The first seven genes in the segment, whose deletion causes Prader-Willi syndrome, are expressed only on the paternal chromosome. It is thus possible for a man with Angelman syndrome to pass the mutation to his daughter, who has Prader-Willi syndrome. This is the first known instance of imprinting in humans.
Features
- Feeding problems (75%) (poor suck, poor weight gain)
- Delay in sitting and walking
- Absent speech
- Poor attention span and hyperactivity
- Severe learning disabilities
- Epilepsy (80%) and an abnormal EEG
- Unusual movements (fine tremors, hand flapping, jerky movements)
- Affectionate nature and frequent laughter
- Wide-based stiff-legged gait
- Below average head size, often with flattening at the back
- Subtle, but characteristic facial features (wide, smiling mouth, prominent chin, thin upper lip, deep set eyes, tendency to hold tongue between the lips)
- Fair hair and blue eyes (60%)
- Poor sleeping pattern
- Squint (40%)
- Scoliosis (curvature of the spine) in 10%
Diagnosis
The diagnosis of AS is based on:
- a history of delayed motor milestones and then later a delay in general development, especially of speech
- unusual movements including fine tremors, jerky limb movements, hand flapping and a wide-based, stiff-legged gait.
- characteristic facial appearance.
- a history of epilepsy and an abnormal EEG tracing.
- a happy disposition with frequent laughter
- a deletion on chromosome 15
Treatment
There is no cure for AS but there are some treatments for the symptoms of the condition. Epilepsy can be controlled by the use of anticonvulsant medication and physiotherapy is important to encourage joint mobility and prevent stiffening of the joints. Occupational therapy, speech therapy, hydrotherapy and music therapy are also used in the management of this condition.
Prognosis
The clinical features of AS alter with age. As adulthood approaches, hyperactivity and poor sleep patterns improve. The fits decrease in frequency and often cease altogether and the EEG abnormalities are less obvious. The facial features remain recognizable but many Angelman adults look remarkably youthful for their age. Puberty and menstruation begin at around the normal time. Although there are no records of an AS individual ever having had a child, sexual development is normal. The majority of those with AS achieve continence by day and some by night. Dressing skills are variable and usually limited to items of clothing without buttons or zips. Most adults are able to eat with a knife or spoon and fork. They can learn to perform simple household tasks. General health is fairly good and life-span near normal. Particular problems which have arisen in adults are a tendency to obesity (more in females), and worsening of scoliosis if it is present. The affectionate nature which is also a positive aspect in the younger children may also persist into adult life where it can pose a problem socially, but this problem is not insurmountable.
External links
- Angelman Syndrome Foundation (http://www.angelman.org)
- International Angelman Syndrome Organisation (http://www.asclepius.com/iaso/)de:Angelman-Syndrom