How ACM is caused
ACM is a genetic, heritable (able to be inherited) condition. ACM is often caused by mutations in the desmosomal proteins. Desmosomal proteins are the bonds, or “glue,” that hold one heart cell to the next. Individuals with ACM are commonly found to have genetic abnormalities in the genes that convert information into code for these desmosomal proteins. When there’s a mutation in these genes, the bonds, or “glue”, that hold heart cells together are defective. Over time, the heart cells can pull apart and be replaced by scar tissue and fat.
In ACM, 5 causative desmosomal genes have been identified, but because only 30% to 50% of patients with AC have 1 of these gene abnormalities, it’s assumed that there are other genes not yet identified. The mutation may be inherited from a parent or may be a result of a new mutation. About 20% -30% of people with ACM have a family history of the disease or of sudden death. Once a person has a mutation, whether due to family history or a new mutation, there is a 50 percent chance that the mutation will be passed on to the children of the person with the mutation.
An individual who has a gene mutation for ACM inherits the risk of having the disease but may or may not develop signs and symptoms of the disease. Other factors such as the presence of an additional gene abnormality or 2 abnormalities within the same class of genes, exposure to certain viruses, athletic lifestyle, etc., can determine whether the individual is affected by ACM. This is an area of active research.
Genetic Testing
Genetic testing can be useful to determine whether a person who is suspected of having ACM has the disease. It’s also useful to identify relatives who do not have signs or symptoms of ACM but have the gene defect. Mutation-specific testing is recommended when a genetic diagnosis of ACM is made in the family member (called the proband) to determine the possible risk in close relatives.
Genetic testing is helpful as follows: if an abnormal gene for AC is identified, it will add confirmation of the disease. If an abnormal gene is present in the patient, and not in the family members, it provides assurance that the family members do not have the disease. And, if no genetic abnormality is found in the patient, it is unlikely that a gene defect would be present in family members.
Who should be tested for ACM?
It is often recommended that all first-degree relatives of a person diagnosed with ACM undergo non-invasive cardiac tests to check for signs of the disease. First-degree relatives are parents, siblings, and children of the individual with the ACM diagnosis.
If genetic testing is not performed in relatives, there may be a psychological impact on these persons who must reconcile themselves to lifelong screenings without the prospect of a definite diagnosis. The other alternative would be to presume that they do not have the disease and accept the possibility that a minority of them and/or their children could experience a tragic cardiac event.
Second-degree relatives (grandparents, aunts, uncles and cousins) don’t need cardiac testing unless they have symptoms.
Clinical genetic testing
Clinical genetic testing for ACM genetic abnormalities is available in the United States and should be performed in certified diagnostic laboratories. It usually requires contributing a small blood sample. The laboratories offering these services vary in price, number of genes screened, and technology used. If you are interested in finding out more about genetic testing for ACM, consult your physician/cardiologist. You can also contact the labs listed below for the costs for the test and more information. There may be other labs available that are not on the list below.
Labcorp
Waltham, Massachusetts 02453
www.labcorp.com
GeneDX
207 Perry Parkway
Gaithersburg, MD 20877
Phone : 301.519.2100
AMBRY Genetics
15 Argonaut
Aliso Viejo, CA 92856
Phone: 949.900.5500
Costs for Genetic Testing
Although fees for genetic testing vary, most genetic testing laboratories accept commercial insurance. A genetic test for ACM can cost as much as $5,400.00 and above. Some laboratories may not accept Medicare or Medicaid. Also, a credit card guarantee may be required for some insurance plans such as Blue Cross and Blue Shield, and so forth. Some laboratories have special arrangements, and a genetic counselor should be engaged in the discussion.
After the signed physician request form has been received, some genetic testing laboratories will offer to contact the patient’s insurance company to determine the out-of-pocket expense after the copay and deductible. If genetic testing is being considered, it may be advisable to seek authorization from one’s insurance company to determine whether subsequent diagnostic tests and treatment may be covered after genetic testing.
Benefits of Using a Genetic Counselor
Genetic counseling is recommended for all patients with a genetically transmitted heart disease. A genetic counselor is a health-care professional who is specially trained in medical genetics and patient counseling. They assist both patients and physicians in the genetic testing process. Some genetic counseling services are offered to patients by telephone. Genetic counseling sessions usually consist of a review of the patient’s diagnosis, obtaining detailed family history, discussion of test results, review of cost and insurance issues, coordination of the testing process, and discussion of test results in family members.
Genetic counselors are trained in both the technical and psychological aspects of genetic testing. Most patients diagnosed with ACM want to understand why their condition developed and their prognosis. They are also concerned about their family members having the disease. Genetic counselors can also help with questions about insurance and assist in completing the paperwork associated with genetic testing. Some companies provide free genetic counseling services to their patients or their physicians.
For more information regarding genetic counseling and/or referrals for a genetic counselor in your area, consult your physician, or contact the National Society of Genetic Counselors at 312.321.6834 or visit www.nsgc.org.
Summary
Presently, the interpretation of genetic tests for ACM is not an exact science and is more complex than for other heart disorders caused by only one gene and for which most patients will have an abnormal gene identified. The clinical application of genetic testing for ACM is that it can be helpful to understand the cause of this disease, to identify family members who are at risk of this condition, for family planning, and for limited prognostic information.
If you are interested in enrolling and/or participating in a National Institute of Health study, consult your cardiologist/physician.