William Smith's disease has grim milestones.

At 2, the Gambrills triplet known as Mick couldn't walk or talk as well as his siblings. In kindergarten, he started losing language and motor skills. At 12, he needed a wheelchair and a feeding tube.

Doctors at Johns Hopkins Hospital dedicated to treating his symptoms said he had an undiagnosed progressive neuromuscular disease.

But a new test may provide something the family has long sought: a name.

"The idea that there is something out there that can tell you [what's wrong] is huge," said Cathy Smith, Mick's mother. "There is a lot of pain that comes from not knowing what is wrong with your kid."

The test, called whole exome sequencing, stems from the decades-long push to map all the genes in the human body and translate that knowledge into diagnostic tools and therapies.

The test has been commercially available for less than three years ,and doctors say it still doesn't offer definitive information for most patients with genetic disorders. The largest published study, by scientists at Baylor College of Medicine in Houston, found diagnoses a quarter of the time, though the success rate appears to be rising.

Data analysis takes three to four months, and the test is so new there is no insurance billing code and often no coverage for the average $7,000 cost even though insurers may pay more for a series of smaller genetic tests and potentially ineffective therapies.

Unlike tests that look for one or a small number of genetic mutations, such as the BRCA test for breast cancer, exome sequencing allows analysis of thousands of genes at once.

The exome is composed of about 22,000 genes, about 1 percent of the human genome. But it is believed to be where functionally important DNA is housed, and where 85 percent of harmful mutations are found.

Read the rest here:
New genetic test helps identify some mystery illnesses

Comments are closed.