Updated: 5/18/2020

Angelman Syndrome

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Snapshot
  • A 2-year-old girl with a history of seizure disorder presents to the pediatrician to establish care, as the family had just moved to a new city. Past medical records show that the patient has been on an anti-seizure medication since 1 years of age. There is no family history of seizures disorders. On physical exam, the girls head circumference is in the 10th percentile. She appears very happy, smiling, and laughing for no appreciable reason. She has not met the expected developmental milestones of a 2-year-old. She is also noted to have hand flapping behavior. She is referred to a geneticist.
Introduction
  • Overview
    • Angelman syndrome is a disorder of imprinting associated with deletion of maternal UBE3A gene
      • previously known as “happy puppet syndrome”
  • Epidemiology
    • incidence
      • 1 in 12,000-20,000
  • Pathogenesis
    • mechanism
      • in patients without Angelman syndrome, in specific areas of the brain, the maternal copy of UBE3A gene is the only active gene
        • if the maternal copy of the gene is silenced, the brain will have no expression of the gene
  • Genetics
    • inheritance pattern
      • sporadic
    • mutations
      • rarely due to paternal uniparental disomy (2 copies of paternal chromosome 15)
      • 70% due to deletion in maternal UBE3A on chromosome 15
      • 10% due to mutation in maternal UBE3A on chromosome 15
  • Associated conditions
    • oculocutaneous albinism
      • due to loss of OCA2 gene
  • Prognosis
    • good prognosis with ability to function
Presentation
  • Symptoms
    • developmental delay
    • intellectual disability
    • speech and motor impairment
    • epilepsy onset by age 3
    • excessive excitable and happy behaviors
      • frequent and inappropriate laughter
      • excessive smiling
      • hyperactivity
      • hand flapping
      • sleep disturbance
  • Physical exam
    • inspection 
      • microcephaly appreciable by age 2
      • ataxia
      • coarse facial features
      • broad thumbs
      • scoliosis
      • strabismus
      • hypopigmentation of skin and eyes
Imaging
  • Radiograph
    • indications
      • evaluate for scoliosis
    • findings
      • curvature of spine
Studies
  • Genetic testing          
    • chromosomal or microarray analysis
    • prenatal testing via chorionic villus sampling or amniocentesis
Differential
  • Prader-Willi syndrome
    • key distinguishing factors
      • silenced paternal genomic material at chromosome 15q11.2-13
      • characterized by hyperphagia and hypotonia
Treatment
  • Lifestyle
    • physical therapy
    • speech and language therapy
    • behavioral therapy
  • Medical
    • anti-epileptics
      • indications
        • seizures
    • melatonin
      • indications
        • sleep disturbance
Complications
  • Seizure disorder
 

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