There are two different types of ALS, sporadic and familial.
Sporadic, which is the most common form of the disease in the U.S., accounts for 90 to 95 percent of all cases. It may affect anyone, anywhere.
Familial ALS (FALS) accounts for 5 to 10 percent of all cases in the U.S. Familial ALS means the disease is inherited. In those families, there is a 50% chance each offspring will inherit the gene mutation and may develop the disease.
To learn more about Familial ALS, please read this helpful resource booklet.
Genetic Testing for ALS
If there is more than one person with ALS and/or frontotemporal dementia in your family or someone was diagnosed at a younger age (such as age 45), you may want to meet with a genetic counselor. Meeting with a genetic counselor involves taking a detailed medical and family history, evaluating risks, and discussing the impact of genetic testing.
A genetic counselor can help you work through the pros and cons of genetic testing based on your concerns and values. Genetic counseling does not always lead to genetic testing.
For more information about genetic counseling or how to find a counselor in your area, please visit www.nsgc.org
Genetic testing can help determine the cause of Familial ALS in a family. Testing is most useful in a person who has been diagnosed with ALS. About 60-70 percent of individuals with Familial ALS will have a positive genetic test result (meaning a mutation has been identified).
Those families with Familial ALS where a mutation is not identified may have ALS caused by a gene or genes that have not yet been discovered. Not having an identified genetic mutation does not eliminate a Familial ALS diagnosis and other family members may still be at risk for developing ALS.
If a mutation has been identified, biological family members who don’t have symptoms can be tested to see if they inherited the genetic mutation; this is called predictive testing. Some medical centers may require a neurological exam, psychological assessment and counseling before predictive testing.
If a person in the family with ALS has a negative genetic test result (no identified genetic mutation), testing family members without a diagnosis of ALS will not provide more information. If no one in the family with ALS is available for genetic testing, a negative test result in an unaffected person cannot be interpreted.
Genetic testing usually involves taking blood or saliva samples. Because this testing needs to be ordered by a health care professional, the sample is usually taken in the doctor’s office or in a lab associated with the doctor’s office. Results can take anywhere from a few weeks to a few months depending on the type of testing ordered. Results should be communicated by the genetic counselor or doctor who ordered the test. This is often done in person at a follow-up appointment or sometimes by telephone.
Because Familial ALS is usually an adult-onset condition, genetic testing of children under age 18 is not recommended.
Genetic testing protocols may differ among clinics. Some clinics may offer testing for different genes, and focus on testing specific patients or people in a family. Other testing may be offered on a research basis only. Test results are not always straightforward. There are some genetic changes that scientists do not understand yet so results can be difficult to interpret.
Genetic testing is a personal choice. Some people with ALS want genetic testing to better understand why they got the disease and help other family members. Some unaffected people want to know if they are at risk for ALS, while others would prefer not to know. Consultation with a genetic counselor can help you decide if testing is the right decision for you.
Some reasons people at-risk for Familial ALS decide to have testing include: getting more information to help make life decisions, allowing time to adjust to the fact they will likely get ALS, reducing anxiety, to help guide reproductive decisions and to provide information for the next generation.
Some reasons people at-risk for Familial ALS decline genetic testing include: the desire to avoid worry about getting ALS, knowing there is currently no cure, and avoiding guilt about passing it on to children or testing negative when others in the family test positive.
Genetic testing may:
Explain if there is a genetic cause of ALS in the family.
Allow other family members to have testing to see if they carry the genetic mutation.
Allow couples planning on having children to pursue prenatal testing.
Genetic testing does not:
Currently change medical treatment.
Diagnose ALS in people without symptoms.
Tell a person without symptoms when they may start showing symptoms or what their progression will be.
DNA banking is a valuable option for people with ALS who do not currently have an identifiable genetic mutation. DNA banking means storing a person’s blood so that it is available for future testing. For more information, you can consult a genetic counselor.
Concerns about Genetic Testing
Genetic testing for all of the currently known Familial ALS genes can cost from about $1600 to $5000. Genetic testing for one gene usually costs $500 - $1500. When the genetic mutation in a family is already known, the cost to test for the familial mutation is usually around $400. Genetic testing is not always covered by insurance. Check with your insurance company about any out of pocket expense prior to testing.
The Genetic Information Nondiscrimination Act of 2008 (also called GINA) is a federal law that protects people from genetic discrimination in health insurance and employment. Genetic information includes both a family history of ALS and a positive genetic test result. Please visit http://www.ginahelp.org for more information.
GINA does NOT cover health insurance eligibility, premiums, or coverage for people who have already been diagnosed with ALS.
GINA does NOT cover life insurance, long-term care, or disability. If you plan to have predictive testing, you should consider having these plans in place prior to testing.
For more information or to find a genetic counselor near you, please visit the the National Society of Genetic Counselors at www.nsgc.org.
For general information about genetics, please visit Genetic Alliance geneticalliance.org and Learn Genetics learn.genetics.utah.edu.