The Genetics of Autism
Genetics have been shown to have a prominent role in the development of ASD. Numerous studies have shown that ASDs have a strong genetic component with most estimating heritability from 70 to 90% 1.
In the vast majority of cases, autism seems to be a multi-gene disease, involving variations of several genes in variable proportions and locations.
A recent study reported that recurrence risk for siblings of affected children is 18.7%, a 20-fold increase compared to the prevalence of autism in the general population. The authors also report differential recurrence risks based on gender (25.9% for males and 9.6% for females.)2.
While many studies have demonstrated a strong genetic basis for autism spectrum disorders, the identification of numerous genetic markers shown to be associated with autism demonstrate a complex inheritance pattern.3Additionally, genetic testing for autism is utilized to identify copy number variants (CNVs) having a strong association with autism. These CNVs are found in less than 10% of affected individuals.4 Adding de novo rare mutations to such CNVs or others chromosomal rearrangements only explain 10 to 20% of autism cases.4
Recently, a number of common genetic variants or SNPs (single nucleotide polymorphisms) have been strongly linked to autism.3,5,6 While individual SNPs are not on their own sufficient to be causal, recent studies have shown that the combination of autism associated SNPs may markedly increase the risk of autism in siblings of affected children.7,8
Click here to learn what a SNP is.
- Carayol J, Schellenberg GD, Dombroski B, Genin E, Rousseau F, Dawson G. Autism risk assessment in siblings of affected children using sex-specific genetic scores. Mol Autism. 2011; 2:17. Click here
- Carayol J, Schellenberg GD, Tores F, Hager J, Ziegler A, Dawson G. Assessing the impact of a combined analysis of four common low-risk genetic variants on autism risk. Mol Autism. 2010; 1:4. Click here
- Freitag CM, Staal W, Klauck SM, Duketis E, Waltes R. Genetics of autistic disorders: review and clinical implications. Eur Child Adolesc Psychiatry 2010; 19:169-78. Click here
- El-Fishawy P and State MW. The genetics of autism: Key issues, recent findings and clinical implications. Psychiatr Clin North Am. 2010; 33:83-105. Click here
- Constantino JN, Zhang Y, Frazier T, et al. Sibling recurrence and the genetic epidemiology of autism. Am J Psychiatry 2010, 167:1349-56. Click here
- Miller DT. Genetic testing for autism: Recent advances and clinical implications.Expert Rev Mol Diagn 2010; 10:837-40. Click here
- Marchant GE, Robert JS, Genetic testing for autism predisposition: Ethical, legal, and social challenges, Hous J Health L & Pol’y 2009; 9:203-35. Click here
- Shen Y, Dies KA, Holm IA, et al. Clinical genetic testing for patients with autism spectrum disorders. Pediatrics 2010; 125:e727-35. Click here
- Miller DT, et al. Consensus statement: Chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies. Am J Human Genetics 2010; 86:749:64. Click here
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