One in five healthy adults has at least one genetic variant predicted to cause rare genetic diseases, according to a new study involving whole genome sequencing (WGS). Would-be parents and children are usually tested with WGS only when there’s reason to suspect a rare mutation, but when researchers applied this technique to low-risk adults, they were surprised to find that roughly 22 percent possessed rare genetic variations linked to disease.
“Our study suggests that having a disease-associated genetic variant may be more common than people think,” coauthor on the study Jason Vassy of Harvard Medical School told Fatherly.
Vassy and his team recruited a small sample of 100 individuals and offered them WGS. They analyzed nearly 5,000 genes linked to rare genetic diseases and found that 22 participants had genetic variations consistent with disease. Six months later, all but a handful continued to display no symptoms, but that doesn’t mean some of the participants won’t suffer from diseases related to these variations down the line. Unlike “carriers” who can pass on a genetic disease to their offspring but experience no symptoms themselves, these 22 volunteers possessed all the genetic material necessary for manifest disease. “We wouldn’t really call them ‘carriers’,” Vassy clarified. “Because geneticists use that term to describe someone who has one copy of a genetic variant when two are required to have the disease.”
Given the relatively small sample size (22 people with rare genetic disease-related variants in a sample of 100 does not necessarily indicate that 22 percent of all people possess these genetic variants) and given the relatively advanced age of the participants (40 and 50-year-olds are seldom trying to get pregnant), the implications for young parents worried about passing genetic diseases to their future offspring are limited. Vassy acknowledges this, and stresses that it would be unwise for healthy couples to pursue whole genome sequencing before trying to have children, based on this study alone. In fact, Vassy is currently working on a project that will help parents make evidence-based decisions about genome sequencing. Until then, he says, all such choices should only be made after consulting with a trusted doctor.
“As with any reproductive decision-making, the decision of whether and what kind of genetic testing to pursue should only come after a patient-provider discussion,” Vassy says.