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 "Ultimately, what we want to do is subcategorize different forms of
autism so we can give specific kinds of treatments," said study
author Stephen Scherer, of the Hospital for Sick Kids in Toronto.
People with an ASD may have difficulties with social, emotional and
communication skills. They may also repeat certain behaviors and
have different ways of learning.
Scherer and colleagues screened 258 unrelated Canadian children with
ASD diagnoses using "chromosomal microarray analysis," which looks
for duplicated or missing segments of a chromosome, where genes are
located.
Overall, 9.3 percent of the children had random or inherited genetic
mutations that could help to explain their ASD.
Ninety-five children were also screened with one of the most
extensive genetic tests available known as whole-exome sequencing,
which found genetic mutations in 8.4 percent.
When the results were combined, mutations were found in 15.8 percent
of children.
Only two children had positive findings on both tests. "You need to
do both tests, because they produce non-overlapping data," Scherer
told Reuters Health.
The children were also examined for physical abnormalities. While
37.5 percent of those with the most abnormalities had genetic
mutations that could explain their ASD, that was true for only 28.6
percent of kids with a moderate number of physical abnormalities and
6.3 percent of those with the fewest abnormalities.
It's possible, therefore, that a physical exam might someday be used
to help predict which children with an ASD are most likely to have
an underlying genetic mutation, the researchers write in JAMA.
A lot of parents want to know the likelihood of another child of
theirs being born with an ASD, said Dr. Catherine Lord, who directs
the Center for Autism and the Developing Brain (CADB) at Weill
Cornell Medical College and New York-Presbyterian in New York City.
But Lord, who was not involved with the new study, cautioned that
these types of genetic results might not do much for the children
right now.
"In terms of what this is going to do to change a child's life, in
many cases it’s not going to change much," she said.
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Still, the new findings are important for the general public,
because they start to show what families might be able to learn from
this kind of testing, Lord said.
While chromosomal microarray analysis is available in most major
medical centers, Scherer also cautioned that whole-exome sequencing
is still a few years away from being available outside of research
settings.
Each test can also cost about $1,000, according to online estimates.
Scherer also said genetic counseling, which guides patients and
their families before and after genetic testing, is critical for
these kinds of screenings.
"Having these tests done is critical and they’re going to be
helpful, but the data has got to be delivered to them in a way they
can understand and utilize it," he said.
Lord said the new findings may encourage families to participate in
large studies, which will provide researchers with data to identify
genetic mutations that may someday help shape the treatment of
people with ASDs.
"I think is would encourage families to give researchers the benefit
of doubt if they have the energy and time to participate in the
studies, because we need the information," she said.
The U.S. Centers for Disease Control and Prevention estimates the
rate of ASD at one in 68 U.S. children, with cases about five times
more common among boys.
SOURCE: http://bit.ly/1IFIvYc and http://bit.ly/1IFIxQ7 JAMA, online
September 1, 2015.
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