The cause of autism spectrum disorders (ASDs), the fastest growing developmental disability in the United States, is still a big mystery. While there’s clearly a genetic component, only 15 percent of people with autism have a known genetic cause. But researchers believe that a much larger percentage of autism can be chalked up to genetics. Now, Children’s Hospital Boston and Autism Consortium researchers have shown that a new genetic test, which samples the whole genome, may work three times better than standard tests.
Families expecting a child who have a family member with an ASD sometimes seek genetic testing to determine whether their baby is at risk. In a child who’s already affected, genetic testing can explain why the child has autism and let the parents know how likely it is that other children in the family could inherit the genetic risk for autism.
But up until now, the recommended genetic tests (karyotyping to look for chromosomal abnormalities and testing for Fragile X, the single largest known genetic cause of ASDs) aren’t that helpful as they are limited in their scope and often come up negative. Now, Children’s Hospital Boston and Autism Consortium researchers have shown that a new genetic test that samples the entire genome, known as chromosomal microarray analysis, has about three times the detection rate for genetic changes related to ASDs than standard tests. Publishing in the April issue of Pediatrics, the authors urge that CMA become part of the first-line genetic work-up for ASDs. Because it is new, CMA is often considered a second-tier test, which means it isn’t always covered by health insurance.
Identifying a specific genetic cause for ASD helps with patient care by alerting clinicians to other medical problems that may be linked to that particular type of deletion or duplication. This type of genetic testing may eventually lead to specific treatment approaches for each sub-type of autism.
The study’s co-senior authors, Bai-Lin Wu, PhD, director of Children’s DNA Diagnostic Lab, and Children’s clinical geneticist David Miller, MD, PhD, believe there’s great value in slowly pinpointing genetic causes, no matter how long takes. “I don’t think we’re going to find one cause that explains 50 percent of autism,” Miller notes. “But even if it’s 1 percent at a time, we’ll eventually be able to figure out what’s going on in each particular family.”