Fragile X positivity in Chinese children with autistic spectrum disorder.

Chromosome analysis was performed in 105 Chinese children (96 boys, 9 girls) with autistic spectrum disorder to assess fragile X positivity. Seventy percent of these autistic children were mentally retarded. None of the children in the infantile autism group (N = 75) had fragile X positivity. Two boys in the autistic condition group (N = 30) had clinical features and chromosomal positivity for fragile X syndrome. The low (2%) prevalence rate of fragile X positivity in children with different degrees of expressivity of autistic features may be related to other factors rather than to pure autistic characteristics per se.