Tall, abnormal behavior The incidence is 1:840 in newborns. Only few patients are found in children and adults, as most phenotypes are normal. Abnormal manifestations Growth: accelerated growth in mid-childhood; Behavior: mental retardation, normal IQ, slightly lower than brothers, slightly floppy, poor motor coordination, late speech, half learning disabilities; Dentition: large teeth; Face: prominence between eyebrows, asymmetry, long ears; Skeleton: its length increases compared to its width, manifested in the skull, hands, feet, etc.; Skin: marked nodular acne in adolescence. Natural history Birth height and significant growth by age 5 or 6 years, but not strong and poorly coordinated behavior. Behavioral problems, including easy distraction, high excitability, and a tendency to lose temper in childhood and early adolescence, gradually grow older and can control their emotions without major problems. Sexual maturation may be six months late. There is normal heterosexuality. Most can have children with normal chromosomes. However, their offspring have a high risk of miscarriage, intrauterine death and chromosomal abnormalities. There is a low risk of gonadal tumors.