Lisa Bond, a single mother of two in Campbellford, Ont., waited years to learn both her children had autism spectrum disorders. When a developmental specialist tried to assess her younger son Joshua when he was three, he refused to co-operate. Ms. Bond was told to bring him back in six months. Her son, now 14, was 6 when he was diagnosed.
“It was a nightmare for me, constantly going to doctors,” she said. “Now they realize the quicker we get to these kids the better. … There’s that critical time between the ages of 2 and 5.”
A genetic test, she said, could also tell parents about the specific problems their child is likely to encounter. As part of the study, Ms. Bond learned her son has a region of chromosome 16 deleted, which helps to explain why he also has trouble with his spine, walking and swallowing.
“Now we know this chromosome affects so many systems,” she said. “Hopefully someday parents will be able to hear when their child has autism that he might need a speech therapist, but also a heart specialist.”
Ms. Bond’s eldest child Rebecca, now 17, was diagnosed at 12 with Asperger syndrome, a high-functioning form of autism characterized by normal intelligence, striking talents and obsessive interests (in Rebecca’s case, dinosaur teeth). But she does not carry the same genetic mutation as her younger brother.
Some experts believe the increased prevalence reflects better detection and the trend to diagnose autism over other developmental disorders. Others suspect environmental triggers, such as toxins or food allergies. But no one doubts the major role genes play, or that environmental forces influence them. Autism disorders run in families, and if one identical twin develops an ASD the chances are as high as 92 per cent the other twin will as well.
For some people at the mild end of the autism spectrum, and their advocates, who see their unusual traits as characteristics that enrich society, the notion of screening for autism is highly controversial.
Dr. Szatmari said the genetic research is not geared “to eradicate the disorder, to get rid of it, but to ease the suffering earlier, when the brain is developing, and give [children] the skills to cope as they grow up.”
Still, he acknowledged the findings “can have big effects on family planning.”
Scientists used the latest microchip tools to scan the DNA of nearly 1,000 people with autism and 1,200 controls. Such scans are not designed to pick up specific mutations, but rather cover the whole genome and highlight areas where large chunks of DNA are deleted or repeated like a record skipping.
These types of hiccup mutations are known as copy-number variants, or CNVs. Researchers found that people with autism have more CNVs in their genes than controls.
In all, the study, spearheaded by post-doctoral research fellow Dalila Pinto at Sick Kids, identified more than 100 genes affected in the people with autism, many of them forming part of a network that governs how brain cells grow and talk to each other.
Some of these genes include those that overlap other forms of intellectual disabilities and certain drugs already exist to treat them.
But where researchers expected to find that a common set of CNVs would explain autism disorders, they instead found unique patterns of CNVs in each case. Most had been inherited, but some are new mutations that sprung up during conception. Researchers are now investigating whether the age of the parents increases the risk of these glitches.
Dr. Scherer said these types of mutations are rare because people with autism do not tend to have children who will go on to spread it through a population. In cases where one parent has passed down a CNV, it may be that something in the environment has transformed it from a mild trait to full blown autism. Or, he said, it could be another inherited trait has combined to result in the disorder.
Scientists suspect the genetic pattern found in autism, similar to the model uncovered in schizophrenia, will also be detected in most other neuro-psychiatric conditions.
