With laughing, even at someone's pain, is a symptom. klinefelter syndrome angelman syndrome down syndrome tourette syndrome

With Angelman's syndrome, laughing, even at someone's pain, is a symptom. 
The Angelman's syndrome is a genetic disorder that mainly affects the nervous system. It is characterized by severe developmental delay and speech impairment, balanced and behavioral disturbance.Many children with Angelman syndrome have a facial appearance with a wide, smiling mouth, deep set eyes and prominent chin.

Could you elaborate?