Genetic Testing for Autism: 6 Surprising Things You Should Know

Autism spectrum disorder (ASD), or simply autism, is a developmental disorder. It affects both verbal as well as nonverbal communication, behavior, and social skills. Children with autism look at the world and what is happening around them much differently than other kids. Some behaviors that are associated with autism include having difficulty dealing with change as well as displaying restricted, stereotyped, or repetitive interests. Because autism is different for every child, and there is a wide range of symptoms, the disease is generally called ASD.

While we don’t exactly know the cause of autism spectrum disorder, we do know that it is likely to be a combination of things. For one, kids with ASD are much more likely to have a family member who suffers from ASD than those who don’t. This points to genetics as an important factor in ASD. Also, some children may have a medical condition that is associated with ASD.

According to international sources, about 1 in 100 children has ASD and boys are 4 times more likely than girls to have it. Even though it may seem like more children suffer from ASD now than in the past, this may be because of better awareness and recognition of ASD than before. This could also mean that there have been changes in how ASD is diagnosed, which means we are now much more likely to recognize its symptoms than before and are much more sensitive. Therefore, more diagnoses are being made than before. ASD occurs both in children as well as in adults. The condition is typically diagnosed in childhood, even though some individuals are diagnosed during their teenage years or even in adulthood. One way to test for ASD is through genetic testing.

There are many genetic tests available for autistic children. These tests test the kid’s DNA in order to find possible changes in the genes that may be behind ASD symptoms. The tests are based on so-called clinical microarrays. They compare an individual’s genes to a reference genome (healthy DNA). This helps detect either duplications (simply put, too much DNA) or deletions (not enough DNA) that may be connected to autism.

Genetic testing makes it possible for parents to find out what is behind their child’s autism and developmental delay. This makes it possible to get the most appropriate and most quality medical care. In addition, parents can find out a few other things. For one, genetic testing lets them know about the likelihood that another family member may have autism. They can also find out about other potential diseasessuch as heart disease or seizures that happen along with their child’s delay. Last, but not least, genetic testing informs parents about the progress of autism. In other words, they are informed about how, when, and how quickly their child’s autism will develop and what to expect in the future.

There are six surprising things about genetic testing for autism you should know.

First Line of Genetic Testing

Chromosomal microarray analysis (CMA) is considered the first line of autism genetic testing. It can pick out small regions of abnormalities in chromosomes that are made up of DNA. These small regions of DNA are called copy number variants (CNVs). A CNV is a change to the expected amount of DNA in a chromosome. Healthy individuals typically have two copies of chromosomes—each inherited from one biological parent. When a region of a chromosome either has fewer or more than two copies, it is referred to as a CNV. An extra copy is a duplication while a missing copy is a deletion. These are small chromosomal regions that the CMA test can pick out.

Inherited Disease? Maybe not Entirely

People with autism carry more de novo CNVs, meaning they are not inherited from parents. De novo is a Latin term that literally means ‘from new.’ In terms of autism, de novo means that the genetic mutation has no definable background—it just happened spontaneously. This case of autism accounts for a total of 5–10% of autistic individuals is a lot more than expected, considering that it is largely thought of as an inherited disease.

Figure 1. What causes autismFigure 1. What causes autism?

70% accuracy?

Physicians call genetic test results as a likeliness that a child may have ASD. What that means is that, if your child does not have symptoms and the test is positive, it means that there is still a high chance the child may not develop ASD. In other words, all genetic tests are said to be 60–70% accurate so far. However, there may be an improvement on the way (see below).

90% accuracy?

Scientists have recently developed a blood test that looks for abnormal proteins in those with autism. Their research was based on blood from both autistic and healthy kids. They report the test to be able to predict whether a kid does or does not have autism with 87–90% accuracy. So, there is hope!

It’s all about Timing

Finding out about whether or not your child’s genes carry a gene for autism can make a big difference in a child’s life. For example, if parents find out early on about a genetic mutation in any of the several genes that are associated with autism, interventions can be started before it’s too late. Interventions include any of the exercises that immediately begin improving possible developmental delays, such as physical therapy and feeding therapy.

So Many Genes

A whopping total of 400 genes and several CNVs together can result in a diagnosis of high to moderate risk for autism. However, each of these genetic mutations on its own does not make up more than 1% of the total cases of ASD.

Figure 2. A very complicated figure to illustrate that there are so many genes involved in autism.Figure 2. A very complicated figure to illustrate that there are so many genes involved in autism.

Laura Day
 

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