Variants in HEY2 have mainly been investigated in an extended family with cardiovascular defects, including congenital heart defects, a dilated thoracic aorta, valve defects or an irregular structure of the heart muscle. Two inherited variants (‘homozygosity’) have resulted in severe congenital heart defects in all 3 individuals identified, whereas one inherited variant (‘heterozygosity’) seems to lead to cardiovascular defects in some, but not all individuals. We hope to learn more about this gene in the future, especially what the consequence is for individuals with one inherited variant in HEY2. Therefore it is important to collect as many information as possible. The prevalence remains to be determined, but is likely to be low.