New gene-based tests that map out a person's entire genetic code can help explain why a child has birth defects or developmental delays, but they are also exposing some dark family secrets.
Researchers at Baylor College of Medicine in Houston recently started using such tests and have uncovered several cases of likely incest, says Dr. Arthur Beaudet, chairman of molecular and human genetics at Baylor, who wrote about the problem on Thursday in the journal Lancet.
The tests, called single nucleotide polymorphism-based arrays, allow doctors to scan a child's genome for extra or missing copies of genes that could explain their disability.
But they can also show large, identical chunks of DNA that a child might have inherited from two closely related relatives, such as a father and daughter, raising social and legal issues that institutions and the scientific community must address, Beaudet said in a telephone interview.
"The concern mainly stems from the possibility of children being sexually abused in the home, most often girls between 12 and 16 years of age," he said.
Disabilities are frequent in children born of incestuous liaisons. In the past, doctors may have suspected a child was the product of incest, Beaudet said. "Now we have a routine test that we do in children with disabilities that makes it obvious."
U.S. doctors are legally and ethically bound to disclose cases of suspected child abuse to authorities.
"Most often we don't really suspect it and the lab result come as a surprise," Beaudet said.
'A Little Agony'
Nancy Spinner, a professor of pathology at the University of Pennsylvania School of Medicine, said her team had encountered two cases of incest since it began using SNP-based arrays from gene sequencing company Illumina Inc in May 2008.
"In both cases, you see it and it causes you a little agony because you realize it could be a big problem. But when we contacted the physician to learn more about the case, in both cases it was known," Spinner said in a telephone interview.
"In one case, the father was incarcerated for rape. In the other case, there was a known product of incest," she said.
Spinner said her lab had yet to see a case in which the incest was not known by the referring physician, but she knows it could happen. "We have discussed this with our medical ethics committee."
Beaudet and colleagues are calling on professional groups to establish guidelines to help in such cases.
Incest cases found in such tests are what researchers call an "incidental finding" and Spinner says they are likely to occur more frequently as scientists begin to explore the power of genomic technology.
Ten years after the first sequencing of the Human Genome, gene tests are finally coming of age as sequencing technology becomes more affordable.
Only a handful of U.S. labs now use the SNP-based arrays routinely. Spinner's lab uses them because they can explain disorders that previously went undiagnosed, and she said many more labs were interested.
"We recognize we will make observations that were not necessarily what we were looking for." But Spinner says it is important information to have.
"Putting your head in the sand does not seem an answer to me, but it does mean we have a lot of work to do to be sure we don't do any harm with these technologies."