We have over 20,000 different genes in the body. These genes are like instruction manuals for how to build a protein, and each protein has an important function that helps to keep our body working how it should. The KCNH2 gene makes a protein called the KCNH2 protein that helps to build potassium channels in the body. These potassium channels allow cells to make and transmit signals which help to recharge the heart after it beats, which in turn helps to keep the heart beat at a normal rhythm. The potassium channels that are made by the KCNH2 gene are primarily in the heart muscles.
If someone has a harmful change (called a pathogenic variant) in one of their KCNH2 genes, then their body is not going to make enough of the KCNH2 protein as it should. If there is not enough KCNH2 protein, then there will not be enough potassium channels. This would mean that the heart’s ability to send these signals is not going to work as well as it should. This can lead to several different types of health concerns, including Long QT syndrome and familial atrial fibrillation.
Pathogenic variants in the KCNH2 gene are passed through a family in an autosomal dominant pattern, meaning that anyone who carries the variant has a 50% chance to pass it down to any children they have. Women and men both have the KCNH2 gene and have the same chances to inherit and pass down pathogenic variants.
If someone inherits a pathogenic variant from BOTH of their parents, they have zero working KCNH2 genes. This can cause an autosomal recessive condition called Jervell and Lange-Nielsen syndrome, which causes Long QT syndrome and profound hearing loss from birth. Approximately 10 percent of cases of Jervell and Lange-Nielsen syndrome are caused by non working KCNH2, while the rest are caused by non working KCNQ1 genes.
Genetic testing for pathogenic variants in KCNH2 is currently available, but there are a few different ways to approach testing: