Autism Spectrum Disorder is a neurodevelopmental disorder characterized by impaired social communication and repetitive or stereotyped behaviors. According to the World Health Organization , the prevalence of Autism Spectrum Disorder is one person in 160.

Genetic and non-genetic factors would contribute to the development of autism. However, the molecular mechanisms of ASD are not clear and successful treatments are still under research. Autism Spectrum Disorder can occur due to exposure to environmental pollutants which lead to epigenetic changes like DNA methylation, acetylation and post-translational modifications. However, the role of epigenetic changes in Autism Spectrum Disorder is still debated.

Epigenetic mechanisms represent a link through which environmental factors interact with the genetic factors resulting in modification of Autism Spectrum Disorder risk through changes in gene expression. DNA methylation and histone deacetylation are two major epigenetic mechanisms that regulate the gene expression at successive stages of brain development.

Brain derived neurotrophic factor is responsible for brain development. Altered BDNF levels and expression may be closely associated with Autism Spectrum Disorder. . Glial fibrillary acidic protein is the hallmark intermediate filament protein in astrocytes, the main type of glial cells in the central nervous system. Interestingly, Glial fibrillary acidic protein is a marker of astroglial activation and the recent data indicated that Glial fibrillary acidic protein could be implicated in the pathophysiology of autism. However, the underlying mechanisms for the role of brain derived neurotrophic factor and glial fibrillary acidic protein in autism spectrum disorder are poorly understood.

Inclusion Criteria:

1. - All enrolled children with Autism Spectrum Disorder will be:

   1. Exhibit symptoms within the typical triad of autistic traits: communication impairment, social deficits, and ritualistic interests.
   2. Drug-naïve.

2. Children with Autism Spectrum Disorder and controls will be 2-6 years old.

Exclusion Criteria:

The control subjects will also clinically examined by the psychiatrist to exclude any sub-clinical autistic features. Children with Autism Spectrum Disorder and controls will excluded from the study if

1. They receive treatment for any reason.
2. -Endocrinological disease, mental retardation, communication disorder, psychotic disorder, attention deficit hyperactivity disorder and learning disorders seen in the children or their family members.

The children attending the pediatric clinic at Assiut University Hospital