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."

Revelations About Heredity Could Create Stigma, Distress and More

Such revelations could cause harm "in the form of stigmatization, emotional distress and criminal accusations," Beaudet and his co-authors wrote in the correspondence appearing in the journal. They suggested that the American College of Medical Genetics, American Society of Human Genetics and European Society of Human Genetics draft practice guidelines addressing consent, disclosure and reporting.

Amy L. McGuire, an attorney who is an associate professor of medicine at Baylor's Center for Medical Ethics and Health Policy, said that as soon as geneticists learned that incest appeared to be an issue for some of their young patients, a committee of ethicists, geneticists and attorneys began "to think through the issues, looking at the laws and some of the ethical considerations related to this and coming up with a policy that the hospitals can use to manage these cases when they come up."

Even with genetic evidence that a child's mother and father are biologically related, "you can't tell from the test definitively who the biological father is," McGuire said. "If there's multiple first-degree relatives, you wouldn't be able to discern whether it was dad, or a brother. That's what makes it difficult to develop general, definitive practice guidelines. Like most areas of medicine, it really depends on the circumstances of the case before you."

In 40 years of doing clinical genetics, Beaudet said he occasionally saw a child whose mother and father were close relatives. But growing use of genetic testing that analyzes single-nucleotide polymorphisms (SNPs, pronounced "snips"), which are variations in single building blocks of DNA, can inadvertently reveal the secrets of a child's birth. That is forcing health professionals to consider the most ethical ways to handle potentially incriminating or otherwise damaging information.

Beaudet said that because doctors are legally compelled to report child abuse to authorities, they need to report incest involving underage mothers, and must ascertain if older mothers were minors at the time of conception. Hospital committees that handle suspected abuse must consider how to protect a mother if she risks returning to an abusive home life.

"Mostly we're dealing with young girls in the home who are probably being sexually abused by their father," Beaudet said in an interview. "They're carrying the babies to term, and they're probably being told that if they tell anyone about anything, they'll be harmed or injured.

"It's not so unusual to have a girl have two or three children with her father," Beaudet said. "If you discover the first one, there's some potential to stop the second one."

He cited one case in which "there were at least three and maybe four girls who were having multiple children with their father. He was in and out of jail. The children were showing up at genetics clinics for obvious reasons."

Beaudet and his colleagues decided to go public to discourage, if not stop incest. "Maybe the people who are the offenders are not amenable to the kind of education we'd like to get out, but ... if this happens and there's a child born, it may well uncover this and get the offender in trouble."

Similar Stretches of DNA from Mom, Dad Don't Always Signify Incestuous Relationships

Lynn Jorde, president of the American Society of Human Genetics, said a society committee that deals with social, legal and ethical issues will consider the legal and ethical ramifications of "detectable incest, especially when there is the possibility that someone may have been abused as a minor." He said it could be "scientifically important to know...if we take a large collection of children with, say, developmental delay, how often do we see incest or just consanguinity?"

Jorde, chairman of human genetics at the University of Utah School of Medicine, said that in most cases where first cousins mate, "most offspring are perfectly healthy," and he worried that some of the genetic test results could make families worry unnecessarily.

Nancy Spinner, director of the Clinical CytoGenetics Laboratory at The Children's Hospital of Philadelphia, said the lab's administrative team flags test results where large regions of genetic material inherited from each parent appear the same. She said that among 4,500 cases completed since 2008, the lab found "two clear cases of incest, but after we agonized and discussed it with the physician, they were both known. One father was incarcerated; in the other case, it was known to the family. We will see what happens with a third case we have, which is in the lab right now. It's not even completed yet."

Like Jorde, Spinner cautioned that mothers and fathers can share large amounts of DNA without their relationship being incestuous. "You can have people who are pretty related, but it doesn't mean it's incest per se. Some populations get so inbred, you can have double-first-cousin marriages." Therefore, it's crucial to first review the findings "and make sure you're comfortable that this could really be incest."

Jorde and Spinner noted that more consumers are paying commercial enterprises like "23 and Me" for what Jorde called "recreational genetic testing" to learn about disease risks, ancestry and traits like baldness. Those findings are based on the same kinds of genetic analyses that the university labs use, and "from that information you could certainly deduce parentage," Jorde said.

He recently co-authored a study with data "where you can see if people are third cousins or fourth cousins" that he said could be useful in missing persons cases, or cases where an entire family has disappeared and the only relatives whose DNA is available for comparison might be first or second cousins.

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"The bottom line is we want to be sure that the science is considered carefully and that we contribute to making good, sound scientific judgments and the many legal and ethical issues are considered appropriately," Jorde said.

The American Society of Reproductive Medicine already has been dealing with issues of consanguinity that could arise if children of sperm donors or egg donors met and unknowingly mated with their half-siblings. ASRM guidelines advised limiting pregnancies per sperm or oocyte donor to 25 within a population of 800,000.

Beaudet's publication in The Lancet was accompanied by a graphic depiction of DNA from a 3-year-old boy with multiple medical problems, in which identical genetic regions from his mother and father were depicted as vivid green blocks on his chromosomes.

Asked what he thought the first time he saw such results, Beaudet said: "It is very striking. I've thought, looking at these lab results, these images, it would be fantastic if we could get Mendel and Darwin and other famous geneticists to be able to see what we see today.

"But socially," he said, "it's a disastrous image."