FISH characterisation of an identical (16)(p11.2p12.2) tandem duplication in two unrelated patients with autistic behaviour

Refined molecular cytogenetic characterisation of unrelated patients with autistic behaviour carrying a familial (mother and daughter) or presumptive de novo duplication in chromosome 16p showed the same genomic region (16p11.2R16p12.2) involved in a direct duplication extending for about 8 Mb. The duplication endpoints were found to map within duplicons located at 16p11.2 and 16p12.2, suggesting that the pathogenetic mechanism leading to the duplication is non-allelic homologous recombination between low copy direct repeat elements. The clinical phenotypic spectrum of the reported patients was compared with the aim of revealing genotype-phenotype correlation. The only clinical feature shared by the 16p11.2R1612.2 duplication carriers is autistic behaviour, although different grade impairments in the social interaction and communication domains characterised both the unrelated and the related patients. This finding suggests that dosage sensitive genes within 16p11.2R1612.2 may be involved in the susceptibility to autism spectrum disorders.