Familial hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy (HCM) is inherited in an autosomal dominant manner. This means that having only one changed (mutated) copy of the responsible gene in each cell is enough to cause features of the condition. When a person with an autosomal dominant condition has children, each child has a 50% (1 in 2) chance to inherit the mutated copy of the gene.

In rare cases, a person with familial HCM has a mutation in both copies of the responsible gene, which leads to more severe signs and symptoms.^[1]

Familial hypertrophic cardiomyopathy (HCM) is caused by mutations in any of several known genes, and possibly other genes that have not yet been identified.^[1] Genetic testing for HCM is most informative as a "family test" rather than a test of one person. Results are most accurately interpreted after merging both genetic and medical test results from multiple family members. Ideally, the family member first having genetic testing should have a definitive diagnosis of HCM and be the most severely affected person in the family. Genetic testing of at-risk, asymptomatic relatives is possible when the responsible mutation has been identified in an affected family member. Testing should be performed in the context of formal genetic counseling.^[2]

An algorithm showing a general approach to finding the specific genetic cause in people with HCM can be viewed here.

The Genetic Testing Registry (GTR) provides information about the genetic tests for familial HCM. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

As is often the case with genetic testing in general, there are benefits and limitations of genetic testing for familial HCM. Testing may confirm the diagnosis in a person with symptoms, and may help to identify family members at risk. However, results are sometimes unclear; testing cannot detect all mutations; and results cannot be used to predict whether a person will develop symptoms, age of onset, or long-term outlook (prognosis).^[2]

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.