Scientists have found a way to explain why a heart condition called hypertrophic cardiomyopathy (HCM) can present so different in family members that carry it. The disorder causes the heart muscles to thicken, and has long been thought to be caused by a rare genetic mutation. But the disease has varying levels of severity in different people, and it can also arise in people that don't have that rare mutation.
Reporting in Nature Genetics, researchers have now determined that common genetic variants are involved in the disorder as well. Humans generally carry the same genome, but within that huge genetic sequence are many small variations, some of which are carried by more than one percent of the population. Some of these variants have been linked to a greater or lesser likelihood of some disease, but in many cases, we don't know whether these variations have any impact on their own or in combination with other variations.
This work has demonstrated that common genetic variants can work in combination with rare, disease-causing genetic mutations to influence a biological characteristic. In some cases, individuals with the rare, HCM-associated genetic mutation are protected from the disease by their common variants while in others, the common variants lead to disease susceptibility.
In this study, the researchers compared the genetic sequences of 2,780 people with HCM with 47,486 people that don't have it. It's thought that about one in 500 people in the UK has HCM, but most don't have symptoms. If untreated, it can cause sudden cardiac death.
"It's now time we think differently about the way this hidden heart condition is detected and treated," said Professor Hugh Watkins, Radcliffe Professor of Medicine and Director of the British Heart Foundation (BHF) Centre of Research Excellence at the University of Oxford.
"We now have a new genetic tool that we believe will better predict which members of affected families will have a bad form of the disease, identifying those who need early intervention. It will also take away the worry for many families as it enables us to identify those who are unlikely to pass faulty genes onto their children. This will reduce the need for unnecessary genetic testing and regular follow-ups."
"This research is a major step forward in our understanding of the genetics that underpin hypertrophic cardiomyopathy. It will revolutionize the way we screen people who have family members with this silent killer," said cardiologist and Professor Sir Nilesh Samani, Medical Director of the BHF.
"HCM is one of the most common inherited cardiac conditions, affecting thousands of families across the UK. These discoveries will bring long-awaited answers to many families, and free many individuals from the need for regular clinical checks and the worry of whether they have also inherited the disease."
The study also found that people with HCM due to common variants can prevent the onset of the disease by keeping their blood pressure low.
Sources: AAAS/Eurekalert! via British Heart Foundation, Nature Genetics