Parents of 42 children (ages 2-32) with Lesch-Nyhan disease were questioned concerning the subjects' behavior patterns. Grouping of responses into nine categories of cognitive skills indicated that only one boy showed any significant cognitive impairment. Despite evidence of good cognitive and emotional skills, subjects were academically delayed,…

This final report reviews the second phase of a life-span study of boys with fragile X syndrome (FSX), the most common known inherited cause of mental retardation. Males with the syndrome are more severely affected than females and in males, delays are usually evident in all the developmental domains, although cognitive and communication skills…