Siblings With Autism Display More Differences Than Similarities

Siblings With AutismNew research indicates that the genetics involved in siblings diagnosed with Autism Spectrum Disorder are as diverse as their varying range of symptoms and behaviors. The research has shed light on the ineffectiveness of the current practice of studying an older child to predict the genetic risk of autism of a future sibling.

Autistic Siblings Have More Genetic Differences Than Similarities

A report issued last month based on a study financed by Autism Speaks, revealed that siblings with a diagnosis of autism show more differences than they do similarities. The genetic risk factors of autism widely vary from person to person, even among siblings. In recent years, scientists were able to isolate specific gene mutations that were found to raise the risk of autism. But those account for a small fraction of the cases.

The researchers used a technology referred to as whole-genome sequencing to analyze the genetic material of families with two children with a diagnosis of autism. Rather than sampling just genomes, this method included the entire genetic map, including all biological abnormalities. Their focus was on approximately 100 genetic “glitches” that are linked to the causation of autism. The research found that about 30% of the siblings shared the same mutation, and 70% did not. The siblings who shared the genetic glitch had similarities in habits and social character to one another, whereas those in the 70% category displayed more differences.

A Story Of Three Brothers

A recent article in The New York Times profiled three brothers in the South family from Oakville, Ontario. Mitchell, their eldest son does not have developmental problems and their second child, Cameron was diagnosed with severe autism. According to their mother, Valerie South, before having a third child, they wanted to ensure that Mitchell would not have to solely carry the burden of living with and helping care for Cameron. So they consulted with doctors to assess their risk of having another child with autism. They were told that the chances they would have another child with autism were very small. And if their third child did have autism, they said it would not be a severe case.

Six years later, their third son Thomas was born. Thomas also has severe autism, however is very different from his brother Cameron. Where Cameron is more withdrawn and sedentary, Thomas is more social and outgoing. Their interests differ significantly as well.

Genetics Of Autism Is A Complex Process

Scientists realize now that they may not be able to obtain the predictive results from genetic mapping as they once thought. And using the older sibling to predict the genetics of their siblings is largely ineffective. The results of this study provide a biological explanation of those differences and the hope is that the type of risk prediction used by the South’s doctor will not be relied upon in the future.

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