Maybe it is his engaging personality or his beautiful, sweet smile, but 3-year-old Tyler Davis draws a crowd every week when he attends his physical therapy sessions.

Clay and Stacie Davis of Denver, Colo., say their son, who was diagnosed with Angelman syndrome at an unusually young age – just 15 months – has a glow. "He literally has people who come every Thursday to find him who want to see him," Stacie Davis says. "They always make comments, 'He just made my week' or 'I've been waiting all week to see that smile.''"

Children with Angelman syndrome have a happy demeanor, laughing frequently and flapping their hands when excited. Dr. Harry Angelman described three cases in 1965, calling the children 'puppet children' because of their stiff, jerky gait, absent speech and excessive laughter. In 1982, Dr. Charles Williams, who formed the first U.S. Angelman syndrome research and education organization, suggested the eponym "Angelman" be used to avoid offending families.

Oftentimes children with Angelman syndrome, a genetic disorder caused by abnormal function of the gene UBE3A located on chromosome No. 15, are misdiagnosed as having autism or cerebral palsy.

Davis says one of the greatest challenges is dealing with his son's sleep disorder. "We are up in the middle of the night with him pretty much every night," Davis says. "He might sleep for six or seven hours straight maybe an average of once a month. But otherwise, we are generally up anywhere from 1 a.m. or 2 a.m. in the morning."

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