الفهرس 
Introduction
Autism Spectrum DisorderOnly 14 pages are availabe for public view
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Abstract
Autism Spectrum Disorders is a complex neurodevelopmental disorder. It starts before three years old. ASD is described by unavoidable defect in social collaboration, impedance in verbal and nonverbal communication, and stereotyped forms of interests and exercises. The expanding rate of ASD in the pediatric population and the absence of fruitful therapeutic treatments make ASD a standout amongst the most difficult issue for medication. National Adult Literacy and Learning Disabilities Center 2014, define learning disability as a neurological condition that interferes with an individual’s ability to store, process, or produce information. So, all children with autism have learning disabilities but not all learning disabilities have autism, that’s why it is very important to differentiate between them. Until now, there is no definitive laboratory investigations are used as biomarkers for autism and learning disability. We try in our research to detect the defects in tryptophan metabolism pathway in both autism spectrum disorder and learning disability.
L-tryptophan is an essential amino acid, which has a significant role in neurodegeneration. Only 1–2% of tryptophan is metabolized into the neurotransmitter serotonin, known as a precursor of melatonin. The great amount of the body tryptophan enters the kynurenine pathway and leads to the production of kynurenic acid, kynuramines, picolinic acid, NAD, and ATP a (source of energy) which regulate CNS function. To detect the impairment of tryptophan metabolism, we measure levels of some genes expression which are responsible for regulation of metabolic pathway; they include MAOA, HAAO and AADAT.
The present study was conducted on children diagnosed according to DSM-5 criteria for autism spectrum disorder and learning disabilities. They were selected from patients regularly attending the follow up at the Neuropsychiatric clinic, Pediatric Hospital, Minia University and from Kayan charity for education and rehabilitation of autistic children, Minia Branch, Egypt. This study was performed to detect the gene expression for MAOA, HAAO, AADAT in autism spectrum disorder and learning disabilities among Egyptian children.
Conclusion
The reduction in the expression levels of MAOA, HAAO and AADAT genes which are involved in pathways of tryptophan metabolism can be used as biomarkers for early diagnosis of autism. Also, they can be used to differentiate between autism and learning disabilites as the levels of these genes are normal with learning disabilities. The current study suported the previous ones that claimed older maternal and/or paternal ages in addition to iron diffeciency aneamia along with vitamin D diffeciency as potential environmental risk factors for predisposition of ASD and learning disabilities.
Recommendations
1- To validate these genes as markers, future studies on larger sample size and multi-central studies are required.
2- Similar studies regarding other genes involved in tryptophan metabolism could help in more understanding of the pathogenesis and progression of autism and finding new biomarkers that are more specific and sensitive.
3- Future comprehensive studies on children who suffering from these neurodevelopmental disorders earlier in their lives i.e. once diagnosed.
4- Screening studies concerned about these disabilities should be performed in schools or day cares as routine screening for earlier diagnosis in order to help or rehabilitate these children.
5- Future prenatal screening studies using these genes along with others which were validated or extensively studied could be designed to prevent or decrease the incidence of these neurodevelopmental disabilities. As well, this screening for pregnant mother should measure maternal levels of chemical risk factors such as maternal hemoglobin, iron and vitamin D levels beside others.