Snapshot A 3-year-old boy with a history of seizure disorder and developmental delay is referred to a geneticist for consideration of genetic testing. His pediatrician noticed that he is very hyperexcitable and is constantly laughing and smiling. His parents also report poor feeding, sleep disturbance, and incessant hand flapping and tremors. He is currently taking an anti-epileptic medication as well as melatonin for sleep. His family history is negative for any developmental disorders. 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 ETIOLOGY 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 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 Prognosis Good prognosis with ability to function