Introduction and development: Autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) are two neuropsychiatric disorders beginning in childhood that present a high degree of familial aggregation. ASD is characterised by social interaction and communication disorders, whereas patients with ADHD display persistent inattention and/or hyperactive-impulsive behaviour. With the exception of a few cases of autism in which cytogenetic anomalies or mutations have been reported in specific genes, the aetiology of these diseases remains unknown. This is a group of multifactorial diseases with several genes having a lesser effect and there is also an environmental component. Genetic linkage studies have pointed to about 20 chromosomal regions that could well contain genes that grant susceptibility to autism, to ADHD or to both disorders. The challenge to researchers lies in the clinical characterisation, recruitment of patients with ASD and ADHD, gene dosage quantification studies, comparative genomic methylation and hybridisation in order to identify chromosomal rearrangements in patients with autism and severe mental retardation.
Conclusions: Genotyping large SNP-type collections that are potentially functional in genes that are candidates for these disorders, based on pharmacological, biochemical and neuropathological data together with that coming from animal models and linkage studies in a wide collection of samples from patients and controls, will enable us to identify the genetic components of these pathologies and to define their biological foundations.