Three distinct disorders arise from either deletions or duplications of genetic material at the 15q11-q13 locus: Angelman syndrome, Prader-Willi syndrome, and 15q11-q13 duplication syndrome (dup15q syndrome). Each of these conditions impacts cognitive function and behavior, although with differing severity. This entry describes each of these conditions, including their clinical features, underlying genetic mechanism, and management.

Angelman Syndrome

Angelman syndrome (AS) was first described by British pediatrician Harry Angelman in 1965. He recognized a pattern in three of his patients and wrote a paper describing the “happy puppet syndrome.” The children had epilepsy and intellectual disability and were nonverbal. They had a notable happy demeanor, jerky movements similar to a marionette, and a characteristic facial appearance. Although a great deal has been learned about the pathogenesis of ...

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