SNP Shot: Genomic Insights

Hypertrophic cardiomyopathy (HCM) is a condition where the heart muscle becomes abnormally thick (hypertrophied). When HCM affects multiple family members, it's called familial hypertrophic cardiomyopathy. HCM can also occur in individuals without a family history of the condition; these are considered cases of nonfamilial hypertrophic cardiomyopathy.

In familial HCM, the thickening typically occurs in the interventricular septum, the muscular wall separating the left and right ventricles (the lower chambers of the heart). This thickening can obstruct the flow of oxygen-rich blood leaving the heart, leading to a heart murmur and other symptoms. In other individuals with familial HCM, there is no obstruction, but the heart's pumping efficiency is reduced, also causing symptoms. Familial HCM typically begins in adolescence or young adulthood but can develop at any point in life.

Symptoms of familial HCM vary, even within the same family. Many people with the condition experience no symptoms at all. Others may have chest pain, shortness of breath (especially during exercise), heart palpitations, lightheadedness, dizziness, or fainting.

Although many individuals with familial HCM have mild or no symptoms, the condition can have serious consequences. It can lead to life-threatening arrhythmias (irregular heart rhythms). People with familial HCM are at an increased risk of sudden death, even if they are asymptomatic. A small proportion of affected individuals may develop heart failure, potentially requiring a heart transplant.

Nonfamilial HCM tends to be less severe. It typically develops later in life than familial HCM, and individuals with nonfamilial HCM have a lower risk of serious heart events and sudden death compared to those with the familial form.

Inheritance:

Familial HCM is inherited in an autosomal dominant pattern. This means that having just one copy of a mutated gene in each cell is enough to cause the condition. In rare cases, both copies of the gene are altered, which leads to more severe signs and symptoms. Usually, a person with familial HCM has one parent who also has the condition. Nonfamilial HCM is not inherited. Its cause is complex and likely involves a combination of genetic and environmental factors.