Genetic Investigations into HLHS: Part 1

Often times, especially for mothers, we find a way to blame ourselves for things that happen to our children. When a family receives the news that their child has HLHS, they begin thinking about what could have caused it. How could this possibly have happened? While the exact cause of HLHS is not known at this time, researchers hope to answer that very question.

Discovering the genetic basis for HLHS is the key focus area for Dr. Timothy Olson, a pediatric cardiologist with a research focus in cardiovascular genetics, and his colleagues within the Todd and Karen Wanek Family Program for HLHS at Mayo Clinic.

In an attempt to identify genes that may cause HLHS, the program is performing array comparative genomic hybridization (CGH) testing along with whole genome sequencing in people diagnosed with HLHS along with their families.

Marissa Ellingson, a genetics counselor at Mayo Clinic, explains what array CGH testing can identify, "Each of the millions of cells in our bodies contains genetic information called DNA. DNA is organized on structures called chromosomes. Occasionally, individuals who have health problems have alterations of the chromosomes. Array CGH is a method of genetic testing that looks for missing or extra pieces of the chromosomes. If a patient has an abnormal array CGH, it means that the patient has a missing or extra piece of one of the chromosomes in each one of their cells." Dr. Myra Wick, Assistant Professor of Medical Genetics and Obstetrics-Gynecology, and medical co-editor of Mayo Clinic Guide to a Healthy Pregnancy and contributor to Mayo Clinic Guide – Your Baby’s First Year, tells us what we do know: for HLHS, there is nothing that could have been done to prevent the problem. To date, many different patterns of inheritance of HLHS have been described in various families.

"When parents have one child with HLHS, the risk of having another child with HLHS is believed to be somewhere around 3-8%," says Wick. "Women who have had a child with HLHS should have a fetal echocardiogram performed during all subsequent pregnancies to screen for heart defects. It is also typically recommended that all first-degree relatives (parents, children, siblings) of a patient with HLHS have an echocardiogram to screen for heart defects, which may have gone undiagnosed."