Genetic Tests Can Unearth Family Secrets, Such as Incest

Feb. 10, 2011— -- The genetic tests that have revolutionized the identification and treatment of many illnesses can also unearth family secrets like incest, sparking an ethical discussion in the medical community over how these inadvertent findings should be handled.

At Baylor College of Medicine in Houston, sophisticated DNA analyses used to diagnose such disabilities as birth defects, epilepsy or developmental delays revealed that in some children, about 25 percent of genetic material inherited from their mother was the same as material inherited from their father. That suggested their parents were first-degree relatives -- father and daughter, brother and sister, or mother and son. Children who inherited half as much identical DNA from both parents likely were the offspring of second-degree relatives, such as an uncle and niece. Had the mothers and fathers of these youngsters been unrelated, those same stretches of DNA would have differed.

In the few months that Baylor has been performing these detailed genetic tests, there have been fewer than 10 cases of consanguinity -- the phenomenon of inheriting the same gene variations from two closely related people, said Dr. Arthur L. Beaudet, chairman of Baylor's department of molecular and human genetics. However, wider use of such testing in children with disabilities is expected to identify additional cases of incestuous parentage.

"Although such revelations might provide important diagnostic clues to the underlying disorders, they also raise important legal and ethical concerns," Beaudet and colleagues wrote in the current issue of The Lancet.

Children of first-degree relatives face a risk of disability up to 50 percent higher than that of children born to unrelated moms and dads, Beaudet said. No one has good estimates on the prevalence of children born from incestuous relationships.

"It used to be in the past that occasionally we would be suspicious, or occasionally a child would be brought in, and social services would be involved and tell us," about incestuous parentage, said Beaudet, a pediatrician also trained in genetics. "But now we see a child where we don't suspect that, and the lab result comes back and says … this child is the product of mating between two very closely related individuals."