Scientists have found the genetic defect responsible for one type of ataxia and developed a quick blood test for identifying people who have the brain-destroying disease or are almost certain to get it.
The development of the blood test represents a breakthrough for families with a history of inherited ataxia because it could help them decide whether to have children and make other major decisions about their lives."It's fantastic news," said Donna Gruetzmacher, executive director of the 10,000-member National Ataxia Foundation. "Finally, people can know specifically what kind of ataxia they have in their family."
Ataxia is a slow, progressive disorder that robs people of coordination and can eventually lead to dementia and death for thousands of Americans.
The newly discovered gene, called SCA2, is responsible for what is known as spinocerebellar ataxia type 2. The blood test can identify people who carry the defect and can also distinguish the disease from a host of other nervous system disorders with similar symptoms.
In addition to making the blood test possible, the discovery of SCA2 also could help scientists in their search for a cure and a treatment.
"There is no cure at this point, and there is no way at the moment to alter the course of the illness," said Dr. Stefan Pulst, the lead researcher and director of the Division of Neurology at Cedars-Sinai Medical Center. But he added: "I'm elated that we now have the gene and can start answering the next round of questions."
Pulst was to present his findings Wednesday at the annual meeting of the American Society for Human Genetics in San Francisco.
Scientists previously identified the genetic defects responsible for two other major inherited forms of the disease, types 1 and 3, and developed blood tests for those, too.
Up until three years ago, doctors could diagnose cases of ataxia based on the patient's symptoms, but they had no way of distinguishing with certainty among the many types of the disease, some of which are not inherited. And they had no way of telling which people were at risk of the disease before they developed symptoms.
"It is likely this test will be relevant to thousands of patients with inherited ataxias," said Dr. Daniel Geschwind, an ataxia specialist at the University of California at Los Angeles.
In types 1, 2 and 3, someone who carries one copy of the defective gene will almost certainly get the disease and has a 50 percent chance of passing it on to each child.