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Geneticists Seek Policies for Disclosing Incestuous Relationships Identified by SNP Arrays


By Justin Petrone

While the advent SNP arrays has greatly improved cytogeneticists' ability to identify the causes of developmental delay, the technology can also inadvertently identify children born of incestuous relationships — a fact that has caused researchers at Baylor College of Medicine to call for official guidelines on handling such cases.

Writing in The Lancet last week, the Baylor team recommended that healthcare institutions establish a committee to draft guidelines that deal with issues of consent and reporting of incestuous parental relationships. They also said that existing ethics committees associated with the American College of Medical Genetics, the American Society of Human Genetics, and the European Society of Human Genetics could also draft such guidelines.

According to Arthur Beaudet, chair of molecular and human genetics at Baylor and a senior author on the paper, the issue of identifying incestuous parental relationships is tied directly to the advent of chromosomal microarray platforms in cytogenetics.

"This issue arises because of evolving technology," Beaudet told BioArray News this week. "Previously used tests did not provide this kind of information."

Now, the same SNP arrays that researchers use to assess the cause of developmental delay also provide data indicating whether an individual has been conceived from an incestuous relationship. As Beaudet and his co-authors noted in the paper, SNP-based arrays can identify regions of DNA with an absence of heterozygosity caused by uniparental disomy or identity by descent, and identification of these regions does not require analysis of parental samples.

The Baylor researchers said they have identified several children referred for intellectual or developmental disabilities or multiple congenital anomalies for whom SNP-array analysis revealed large regions of absence of heterozygosity on multiple chromosomes. In some cases, these homozygous regions accounted for about a quarter of the genome, a finding most consistent with the child having been conceived by first-degree relatives, the authors wrote.

They noted that disabilities are known to be frequent in children born of incestuous parentage. According to Beaudet, the "commonly accepted frequency of developmental disability in children born of father-daughter, mother-son, and brother-sister matings is 50 percent."

Beaudet said that Baylor has dealt with several cases of incestuous parental relationships since it began offering chromosomal microarray analysis in 2004. In the paper, the authors describe how the use of a SNP-based array on a 3-year-old boy with multiple medical problems indicated 668 megabases of absence of heterozygosity.

"This finding is consistent with the patient being conceived as the product of a mating between first-degree relatives," the authors wrote, as the coefficient of inbreeding is one quarter, meaning an expected absence of heterozygosity would be around 716 Mb. In comparison, "for matings between second-degree relatives, such as uncle-niece or double first cousins, the inbreeding coefficient would be [one-eighth] and expected absence of heterozygosity 358 Mb," they wrote.

Beaudet said that Baylor has handled instances of suspected incest by questioning other family members and referring the cases to relevant authorities. "In the past, if the mother was a minor, we would have asked a grandmother or guardian about this possibility," he said. "We have called in child protective services to investigate."

The revelation of an incestuous parental relationship might also cause ethical questions for the clinician charged with treating the affected individual, Beaudet said. "Sometimes, the physician already knows that the child was born of an incestuous mating, but at other times, the mother does not tell the clinician," he said.

"Often these births occur because of sexual abuse of minors – father-daughter, mother-son, or brother-sister, and the minor may have been threatened by the abuser," he added. "I believe it is to society’s benefit and to that of the minor that the information comes to light. Then social agencies and legal systems can intervene to prevent further abuse."

According to Beaudet, guidelines should be set by professional societies and institutions on how to react in cases where incest is uncovered by chromosomal microarray analysis.

"In individual institutions, I would like to see specialized teams established that have the expertise and compassion to deal with these cases when incest is uncovered," he said. "That will provide the at-risk minor with emergency protection and ongoing help in this difficult situation."

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In cases where the mother is a minor, clinicians who uncover a likely incestuous relationship could be legally required to report it to child protection services and, potentially, the police, since the pregnancy might have occurred in the setting of sexual abuse, Beaudet said. The physician's duty to report is less clear in cases where the mother is an adult and might depend on whether she was a minor or an adult at the time she became pregnant, he noted.

While there "clearly exists the possibility of harm in the form of stigmatization, emotional distress, and criminal accusations" from the identification of consanguinity by chromosomal microarray analysis, Beaudet said he is opposed to warning the parents of the affected child beforehand that the test can detect incestuous parental relationships.

"Should parents be alerted to the fact that the test might uncover incest? I do not think so," Beaudet said. "When we do a chest X-ray on a child in the emergency room, we do not warn the parents that it might find broken ribs that occur because of child abuse," he said.

He also stressed that such instances of determining incest are rare and that most congenital abnormalities are the results of genetic mutations or rearrangements, deletions, or duplications in the genome.

"This technology represents the biggest improvement in my memory of our ability to detect the kinds of genetic problems that cause developmental delay, intellectual disability, and birth defects," said Beaudet of arrays.

"We can identify 20 to 25 percent of children with severe disabilities in whom no other cause is evident," he said. "Most of these are children who have intellectual disabilities with or without accompanying birth defects."

Have topics you'd like to see covered in BioArray News? Contact the editor at jpetrone [at] genomeweb [.] com.