Variability in the heterochromatin regions of the chromosomes and chromosomal anomalies in children with autism: identification of genetic markers of autistic spectrum disorders.

Cytogenetic and molecular cytogenetic analysis of children with autism (90 subjects) and their mothers (18 subjects) is presented. Anomalies and fragility were found in chromosome X in four cases of autism: mos 47,XXX[98]/46, XX[2]; 46,XY,r(22)(p11q13); 46,XY,inv(2)(p11.2q13),16qh-; and 46,Y,fra(X)(q27.3),16qh-. C staining and quantitative fluorescent in situ hybridization (FISH) were used to demonstrate a significant increase in the frequency of variations in the heterochromatin regions of chromosomes in children with autism as compared with a control group (48% and 16% respectively). Pericentric chromosome inversion 9phqh was not characteristic of patients with autism, while variation in heterochromatin regions 1phqh, 9qh+, and 16qh-were found significantly more frequently in children with autism. These data provide the basis for discussing the possible role of the gene position effect in the pathogenesis of autism and the possible search for biological markers of autistic disorders.