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Human Genome and Clinical Diagnosis: The Yin and the Yang

New Genetic Testing: Unexpected Consanguinity

Bruce Buehler, MD, Pediatrics, General, 05:37PM Mar 17, 2013

    Microarray samples 180,000 known genetic sites. Now that microarray has been coupled with single nucleotide polymorphisms (SNPs), the new testing identifies the target genes and polymorphisms that can indicate loss of heterozygosity -- and possible consanguinity. Testing a child for a genetic syndrome with the new tests can indicate consanguinity without studying the parents. This raises a very significant concern about what to reveal to a family that denies any relationship, such as in first or second cousins. It also raises issues when one of the parents is adopted and had no reason to consider a family relation with the spouse, or in the case of children of sperm donors.

    The important information about consanguinity is the known increase in autosomal recessive conditions and possible clinical implications for the child being tested. This is especially important for metabolic diseases with potential treatment. 

     Previously, if it was suspected that a person had inherited two copies of the gene from the same parent (uniparental disomy, UPD) such as Prader-Willi Syndrome or Angelman's Syndrome, separate tests had to be done. Now, the high-density SNP array will identify most UPDs. This can be very helpful in treatment.

     The dilemma is how a family will react to knowing that they are closely related. Sometimes the family has no concerns due to cultural normality. But for other families it can be devastating. It is now the practice of our genetic team to review this potential information before testing. On two occasions, families decided against testing, without explaining their concerns. 

     The better our genetic testing, the greater the need for informed consent from the family, including the issue of consanguinity. No genetic testing should be done before the family understands some of the unexpected information they may receive.

About This Blog

With the completion of the Human Genome Project and the explosion in genetic technology, the clinician is challenged to apply the results to direct care. This blog is a place to discuss the advantages and disadvantages of the new knowledge, how to present results to families and patients, and how to appropriately apply predictive genetics for treatment. Interpretation of genetic markers for disease, genetic susceptibility, and single gene changes are new concepts that require thoughtful presentation to patients.
Disclosure: Bruce Buehler, MD, has disclosed no relevant financial relationships.Poll: Will you incorporate universal genetic testing as an option to cystic fibrosis genetic testing in your practice? Yes|No|

  • Bruce Buehler

    Bruce Buehler has been practicing pediatrics and genetics for 38 years. He is Professor of Pediatrics and Genetics at University of Nebraska Medical Center and is the former Chairman of Pediatrics at UNMC and Director of the Munroe Meyer Institute for Genetics and Rehabilitation. Bruce Buehler also serves as Editor in Chief of eMedicine Pediatrics.

The content of this blog does not necessarily reflect the viewpoints of Medscape.
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