A "new" chromosome marker common to the Rett syndrome and infantile autism? The frequency of fragile sites at X p22 in 81 children with infantile autism, childhood psychosis and the Rett syndrome.

Chromosomes from 46 autistic, 20 psychotic and 15 Rett syndrome children were cultured in a folic-acid-depleted medium. Nine percent of the autistic, 20% of the psychotic and 40% of the Rett syndrome cases showed a "new" chromosomal anomaly, viz a fragile site at the (X) (p22) location. It is suggested that in some cases of autism/psychosis and the Rett syndrome, there might be a common biological marker for the common type of psychiatric disturbance. However, as the population frequency of the chromosome marker is not yet known, conclusions must be drawn with great caution.