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Gene sequencing solves one-fourth of mystery diseases in kids, adults


October 3, 2013
By By Marilynn Marchione The Associated Press

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Photo credit: Maggie Bartlett, National Human Genome Research InstituteOct. 3, 2013 — (Photo: Maggie Bartlett) They were mystery diseases that had stumped doctors for years – adults with strange symptoms and children with neurological problems, mental slowness or muscles too weak to let them stand. Now scientists say they were able to crack a quarter of these cases by decoding the patients' genes.

Their study is the first large-scale effort to move gene sequencing out
of the lab and into ordinary medical care, and it shows that high hopes
for this technology are finally paying off.

“This is a direct
benefit of the Human Genome Project,” the big effort to decode our DNA,
said Dr. Christine M. Eng of Baylor College of Medicine in Houston.
“We're now able to directly benefit patients through more accurate
diagnosis.”

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She led the study, which was published Wednesday by
the New England Journal of Medicine. It gives results on the first 250
patients referred to Baylor for a newer type of sequencing – just the
DNA segments that hold the recipes for all the proteins the body needs.
That's only about one per cent of the whole genome.

Baylor has sequenced more patients beyond those in the study – 1,700 so far – and found gene flaws in one out of four, Eng said.

That
rate will improve as more genes are linked to diseases, but it's
already much higher than the less comprehensive gene tests done now,
said Rebecca Nagy, a scientist at Ohio State University and president of
the National Society of Genetic Counselors.

“For some of these conditions there could be treatments that are lifesaving,” she said.

Already, three people tested at Baylor were found to have a muscle disorder that can cause respiratory problems and even death.

The condition is aggravated by infections and stress, and there are drugs to treat those and prevent serious episodes, Eng said.

In
other cases, having a diagnosis helped parents like Lindsey and Brandon
Collier decide whether to have more children. The Colliers, who live in
Georgetown, Texas, about 30 miles north of Austin, searched for years
for an answer to what was plaguing their son, Cannon, now four years
old.

“He was a pretty floppy baby” with poor muscle tone and
problems eating, Lindsey Collier said. “We weren't getting any answers
and they were just all over the map on everything they were testing
for.”

“It is a huge weight lifted off our shoulders,” she said of testing at Baylor that found a rare muscle disorder.

Genetic
counsellors said the problem was not likely to occur in other
offspring, so the Colliers had a second child. Their six-week-old
daughter, Smith, is fine, and Cannon is being helped now by intensive
physical therapy and other treatments.

Just having a diagnosis is
very valuable because it ends the expensive and emotionally exhausting
testing that parents go through, said Dr. Robert C. Green, a geneticist
at Brigham and Women's Hospital and Harvard Medical School.

“Many
of these are children or adults that have had a mystery illness for
many years. Their families don't know what it is and they're sort of
desperate for an answer,” and it's not possible to find a treatment
until you find the cause, he said.

In the study of the first 250
patients at Baylor, 62 were found to have gene flaws. In 33 cases, only
one faulty copy of a gene was responsible. In 16 other cases, both
copies of a gene were bad. Four patients had problems in two different
genes. Nine patients had faulty genes on the X chromosome. Since boys
have only one copy of that sex chromosome, those disorders mostly affect
that gender.

Baylor gets revenue from gene testing, and two
study leaders are consultants or paid speakers for gene testing
companies not involved in the study. The government's National Human
Genome Research Institute helped pay for the study, and insurers covered
much of the testing. It cost $7,000 per case, which usually included
sequencing the parents' genes.

The price will drop and the
usefulness will rise over time, Dr. Howard Jacob of the Medical College
of Wisconsin wrote in an editorial in the journal. Several years ago, he
sequenced the genes of a five-year-old Wisconsin boy who suffered from a
rare genetic disease. That unprecedented feat led to a cord blood
transplant and other treatments for the boy.

Other areas of
medicine are exploring gene sequencing. Last month, the government
launched a pilot project to try it for newborn screening. In December,
two studies reported on its use to screen embryos during fertility
treatments, and for figuring out the cause of stillbirths.


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