Hypertrophic cardiomyopathy (HCM) is a condition where areas of heart muscle become thickened and stiff.

The thickening makes it harder for the heart to contract and pump blood. Depending on where the thickening is, it can affect how blood flows out of the heart often referred to as 'HCM with obstruction' or 'HOCM'.

The following diagram, courtesy of Wikipedia, illustrates the difference between a normal heart and one with HCM.

Hypertrophic Cardiomyopathy is the most common type of cardiomyopathy and is caused by variants in genes that encode for proteins that make up the heart muscle. HCM is an autosomal dominant genetic disorder, which means that a person only needs to inherit one copy of the altered gene from one parent to develop the condition. Children have a 50% chance of inheriting the disease from their affected parent. 

The most common genes associated with HCM are MYBPC3, MYH7, and TNNT2. Mutations in these genes account for up to 80% of cases of HCM. However, there are over 30 other genes that have been linked to HCM, and it is possible for a person to have a mutation in a different gene that causes the condition.

HCM can be inherited in different ways within families. Some families may have a single mutation that is passed down from generation to generation, while others may have multiple mutations that cause the condition. The severity of HCM can vary widely between individuals, even within the same family. This is because other genetic and environmental factors can influence how the condition manifests.

For further information about symptoms and treatment click on the following links - Cardiomyopathy UK- Hypertrophic Cardiomyopathy and HCMA