Angelman syndrome

Disease Description (Causes and Symptoms)

• Definition summary: Angelman syndrome is a genetic neurodevelopmental disorder caused mainly by abnormalities in the maternally derived chromosome 15 (15q11q13) region. It is characterized by severe developmental delay, intellectual disability, and a characteristic Down syndrome-like behavioral pattern (distinctive bouts of laughter and a "puppet-like" gait).
• Causes and pathophysiology:
  • Most cases (approximately 75%) are caused by a deletion (microdeletion) of the maternally derived 15q11q13 region.
  • Some cases are caused by paternal uniparental disomy (UPD; 2–3%), imprinting defects (approximately 2%), or mutations in the UBE3A gene within 15q11q13 (approximately 20%).
  • The key pathophysiological mechanism is loss of expression of the maternal UBE3A gene in the brain. Because paternal UBE3A is in a gene-silenced (imprinted/paternally silenced) state in the brain, a functional deficiency results.
• Main symptoms:
  • Severe developmental delay and intellectual disability, with almost no language development (nonverbal communication is used more often than speech)
  • Distinctive bouts of laughter (laughter unrelated to emotion), impaired balance, and ataxia (puppet-like gait)
  • Hypotonia in infancy, followed by frequent seizures (epilepsy) in later stages
  • Microcephaly (or a tendency toward a small head size), facial features (wide mouth, prominent mandible, etc.), and possible hypopigmentation of the iris and retina
  • Characteristic findings may be observed on EEG

Treatment Methods (Standard Treatment, Medication, Lifestyle Management · Precautions)

• Treatment goals: There is currently no definitive cure, and symptom-specific, multidisciplinary supportive care is the standard.
• Rehabilitation:
  • Early intervention: physical therapy (movement and balance), occupational therapy (daily functioning), and speech-language therapy (including augmentative and alternative communication)
  • Behavioral and developmental therapy: educational interventions and special education and therapy plans
• Medication and medical treatment:
  • Seizures (epilepsy): Controlled with anticonvulsants (the choice and combination of medications varies by patient). Levetiracetam, valproate, benzodiazepines, and other medications are generally used, with management by pediatric neurology according to the patient’s condition.
  • Sleep problems: Prioritize sleep hygiene; short-term medications such as melatonin may be considered when necessary
• Follow-up testing and management:
  • Regular neurological follow-up, growth and nutritional assessment, hearing and vision tests, and dental examinations
  • Establishment of response plans for seizures, respiratory problems, and nutritional (swallowing) problems
• Genetic counseling:
  • The family’s recurrence risk varies according to the cause (deletion, UPD, imprinting defect, or UBE3A mutation). If a UBE3A mutation is identified, the recurrence risk may be high; genetic counseling and family testing are recommended.
• Precautions and risk of complications:
  • Manage seizures thoroughly and address seizure triggers such as sleep deprivation and fever
  • Monitor drug interactions and adverse effects (liver function tests, blood tests, etc., when necessary)
  • Pay attention to long-term musculoskeletal management (e.g., gait problems and joints), nutrition, and digestive problems (constipation and dysphagia)
• Research and clinical trials:
  • Research is underway on gene-targeted treatments such as UBE3A reactivation (e.g., antisense oligonucleotides), and indications and results continue to be updated

Checklist Before an Outpatient Visit (Including Items to Bring and Sample Questions)

• Items to bring:
  • A list of currently used medications (dose and timing)
  • Copies of previous test results: genetic tests (chromosome, methylation, and UBE3A sequencing), EEG, and brain imaging (MRI)
  • A seizure diary (frequency, type, duration, and triggers), sleep patterns, and records of eating and swallowing status
  • Developmental history (first smile, rolling over, crawling, sitting, beginning to speak, etc.) and notes on recent changes
  • Documents related to caregivers and education (special education services and rehabilitation program records)
• Information useful to provide during the outpatient visit:
  • When symptoms began and how they have progressed, including whether there has been recent worsening or improvement
  • Family history (similar symptoms or known genetic disorders)
  • The greatest difficulties in daily life (sleep, behavior, communication, movement, etc.)

Examples of General Questions to Ask the Doctor

• What do my (or the patient I care for’s) genetic test results mean? (Which type is it: deletion, UPD, imprinting defect, or UBE3A mutation?)
• What is the recurrence risk (for siblings and future pregnancies) for this type of Angelman syndrome?
• Which medications are recommended for seizure control, and what adverse effects can be expected?
• What aspects of daily life require particular attention (exercise, nutrition, breathing, and sleep)?
• How should the frequency and goals of recommended rehabilitation therapies (physical, occupational, and speech-language therapy) be established?

Examples of Disease-Specific Questions

• Which of the following was identified on genetic testing: a "microdeletion of 15q11q13 (or a UBE3A mutation, UPD, or imprinting defect)"? Based on this result, what is the family recurrence risk, and what additional recommended tests (such as parental testing) are needed?
• Seizures have recently become more frequent. If the anticonvulsant currently being taken is not effective, what is the next step (changing medication, repeat EEG evaluation, inpatient observation, etc.)?