Genetic influences and infantile autism

Abstract

IN his original description of infantile autism, Kanner suggested an “inborn defect”, because symptoms were often present from early infancy. Despite the rarity of a family history of autism and lack of a known increase in parental consanguinity, there are two reasons for suspecting hereditary influences: the 2% rate of autism in siblings is 50 times that of the general population¹, and a family history of speech delay is found in about a quarter of families². Reports of single pairs of twins with autism have not added much to our knowledge of genetic effects because of a bias toward reporting monozygotic (MZ) concordant pairs and because few reports contain both adequate clinical descriptions and evidence of zygosity¹. We therefore undertook a study of a systematically collected sample of 21 pairs of same-sexed twins, one or both of whom had autism as diagnosed by the criteria of Kanner³ and Rutter⁴. The results reported here indicate the importance of hereditary influences in the aetiology of autism.