Abstract: Autism spectrum disorder (ASD) is one of the most common neurodevelopmental disorders representing deficits in socialization, communication impairment, repetitive patterns of behaviors and/or restricted interest. The increasing prevalence of ASD worldwide is most likely due to increasing awareness, widening of the diagnostic concepts and availability of diagnostic framework. It is a genetically influenced disorders caused by factors including genetic, epigenetic factors that affect gene expression and activity and non-genetic factors like environmental exposures. It is widely thought to represent a disorder of connectivity, in which the environment interacts with the genome. It can occur as an association with genetic syndrome, can occur sporadically or may be familial.