Angelman syndrome

Angelman syndrome (AS), also known as 'happy puppet syndrome' (a historical term now considered outdated), is a rare neurodevelopmental disorder primarily caused by loss of function of the maternally inherited UBE3A gene on chromosome 15q11.2-q13. The condition affects the nervous system and is characterized by severe intellectual disability, absent or severely limited speech, movement and balance difficulties (ataxia), and a distinctive behavioral profile that includes frequent smiling and laughter, an easily excitable personality, and hand-flapping movements. Seizures typically begin between 1 and 3 years of age and occur in approximately 80–90% of affected individuals. Microcephaly often becomes apparent by age 2. Sleep disturbances are very common, particularly in childhood. The genetic mechanisms underlying Angelman syndrome include deletion of the maternal 15q11.2-q13 region (approximately 70% of cases), paternal uniparental disomy of chromosome 15 (2–3%), imprinting defects (3–5%), and pathogenic variants in the UBE3A gene (10–15%). The UBE3A gene is subject to genomic imprinting, with preferential maternal expression in the brain, which explains why only loss of the maternal copy leads to disease. Diagnosis is confirmed through methylation analysis, fluorescence in situ hybridization (FISH), chromosomal microarray, or UBE3A sequencing. There is currently no cure for Angelman syndrome, and management is symptomatic and supportive. Seizures are treated with antiepileptic medications, though they can be difficult to control; valproate and benzodiazepines are commonly used, while certain medications such as carbamazepine may worsen seizures. Physical therapy, occupational therapy, and speech/communication therapy (including augmentative and alternative communication strategies) are essential components of care. Melatonin is frequently used to manage sleep disturbances. Several gene therapy and antisense oligonucleotide approaches aimed at reactivating the paternal UBE3A copy are currently under investigation in clinical trials, representing a promising area of therapeutic development.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Angelman syndrome