Angelman Syndrome

Angelman syndrome (AS) is a genetic disorder that primarily affects the nervous system. It stems from the lack of function of part of chromosome 15, specifically due to a deletion or mutation of the UBE3A gene. This gene is very important in brain development, and its absence or dysfunction leads to the characteristic features of the syndrome. Typically, this condition arises from a new mutation rather than being inherited.

A five-year-old girl with Angelman syndrome. Features shown include telecanthus, bilateral epicanthic folds, small head, wide mouth, and an apparently happy demeanour; hands with tapered fingers, abnormal creases and broad thumbs.

Signs and Symptoms

Angelman syndrome manifests through a range of symptoms, which usually become noticeable by one year of age. Common symptoms include delayed development, severe intellectual disability, limited to no functional speech, movement and balance issues, seizures, and sleep problems. Children with AS often display a happy demeanour and have a particular fascination with water.

Consistent Symptoms (100%)

• Severe developmental delay
• Speech impairment, with minimal use of words
• Movement or balance disorder, typically ataxia and tremulous limb movements
• Behavioural characteristics such as frequent laughter, an excitable personality, and hand-flapping movements

Frequent Symptoms (more than 80%)

• Microcephaly by age 2
• Seizures, usually beginning before age 3
• Abnormal EEG with characteristic patterns

Associated Symptoms (20–80%)

• Strabismus
• Hypopigmented skin and eyes
• Tongue thrusting and sucking/swallowing disorders
• Hyperactive tendon reflexes
• Feeding problems during infancy
• Uplifted arms during walking
• Prominent mandible
• Increased sensitivity to heat
• Wide mouth and spaced teeth
• Sleep disturbances
• Frequent drooling and protruding tongue
• Fascination with water
• Excessive chewing behaviours
• Flat back of head
• Smooth palms
• Gastroesophageal reflux disease (GERD)
• Constipation

Cause

Chromosome 15

Angelman syndrome is caused by the lack of expression of the UBE3A gene, located on chromosome 15 (region 15q11-q13). This gene is essential for normal brain development, and its absence or dysfunction leads to the condition. The paternal copy of UBE3A is typically inactivated in certain brain regions through genomic imprinting, leaving the maternal copy as the sole functional version. In AS, the maternal UBE3A gene is either deleted, mutated, or inactivated, leading to the disorder.

Neurophysiology

EEG studies in individuals with AS usually show abnormal patterns that aid in differential diagnosis. These include large amplitude 2-3 Hz rhythms, symmetrical 4-6 Hz high voltage rhythms, and 3-6 Hz activity with spikes in occipital leads during eye closure. These EEG patterns are not directly linked to the characteristic laughter seen in AS, ruling out gelastic seizures.

Diagnosis

Diagnosis of Angelman syndrome involves a combination of clinical features and genetic testing. Key diagnostic criteria include delayed motor milestones, characteristic facial features, abnormal movements, epilepsy, and a happy disposition with frequent laughter. Genetic tests such as array comparative genomic hybridisation (aCGH) or BACs-on-Beads technology can detect deletions or inactivity on chromosome 15.

Differential Diagnosis

Conditions that may present similarly to AS include autism spectrum disorder, cerebral palsy, Rett syndrome, and Prader-Willi syndrome. Accurate diagnosis is very important for appropriate management.

Treatment

Melatonin

There is no cure for Angelman syndrome; treatment is supportive and symptomatic. Anti-seizure medications are used to manage epilepsy, though determining the appropriate medication and dosage can be challenging due to the variety of seizure types in AS. Melatonin is often used to regulate sleep patterns, and mild laxatives may help with constipation. GERD is commonly treated with medications like ranitidine.

Early intervention with physical and occupational therapy is beneficial. Occupational therapists can aid in developing non-verbal communication skills, sensory processing, and fine motor control. Individuals with AS typically have better receptive language skills than expressive ones and can learn non-verbal communication methods such as gestures and sign language. Improvements in living skills and communication are achievable with continued support and therapy.

Prognosis

The severity of AS varies widely. Some individuals may achieve some speech and self-care abilities, while others may remain more profoundly affected. Participation in therapy can improve outcomes in cognition and communication. Seizure frequency and sleep patterns often improve with age, and many adults with AS maintain a youthful appearance. Most individuals achieve daytime continence and can manage simple tasks, though they may face challenges such as obesity and scoliosis. Life expectancy is near normal, with individuals living slightly shorter lives than the general population.

History

Boy with a Puppet

Angelman syndrome was first described by British paediatrician Harry Angelman in 1965, inspired by a painting he saw in Italy. Initially termed "Puppet Children," the name was later changed to Angelman syndrome. Genetic causes were identified in the 1980s, leading to a better understanding of the condition.

Self-assessment MCQs (single best answer)

What is Angelman syndrome primarily caused by?

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Which chromosome is associated with Angelman syndrome?

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At what age do symptoms of Angelman syndrome typically become noticeable?

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Which of the following is a consistent symptom of Angelman syndrome?

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What is a common behavioural characteristic seen in children with Angelman syndrome?

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Which EEG pattern is typically observed in individuals with Angelman syndrome?

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What is a frequent symptom of Angelman syndrome that appears more than 80% of the time?

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Which medication is often used to regulate sleep patterns in individuals with Angelman syndrome?

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What was the initial term used by Harry Angelman to describe the syndrome?

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What is the general prognosis for individuals with Angelman syndrome?

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