Search for DNA markers in two autistic males with the fragile X syndrome.

Kanner (1943) was the first investigator in the field of infantile autism to suggest a genetic predisposition in children who later developed the symptoms of autism. Family and twin studies of autism have shown that autism is occasionally aggregated in families (reviewed by Folstein & Rutter, 1987). These kinds of studies, however, tell us little about the nature of the genetic defect or defects. A number of recent studies have reported an increased prevalence of the fragile X chromosome in autistic populations. A recent review summarized the results of 10 studies of a total of 594 autistic males and arrived at a mean rate of 8.4~ of autistic males having the fragile site 0tregman, Dykins, Watson, Ort, & Leckman, 1987). The meaning of this association is not clear. However, it has been suggested that when a chromosomal abnormality is associated with a disease, a gene causing the disease may be located within the region of the abnormality. Thus, the association does suggest a discrete region of the genome in which to search