Genetics of FTD
After receiving a diagnosis of FTD in a family member, one of the first questions many people have is: Are other members of the family at risk for developing FTD as well?
The answer, like most things related to FTD, is not a simple one. But the good news is that recent advances in science have brought the genetics of FTD into much better focus. In 2012, we have identified the major genes that are involved in FTD and the related disorders and we have a much better understanding of how to assess hereditary risk within a family.
AFTD has worked with the University of Pennsylvania Center for Neurodegenerative Disease Research to publish a booklet called Understanding the Genetics of FTD: A guide for patients and their families. You can download the booklet here or request a print copy. For five or fewer copies, send an email to firstname.lastname@example.org with your request and address. For orders of six or more booklets, use our on-line order form. A $1.00 per booklet fee is charged to cover shipping and handling.
Some of the most important points from the booklet are excerpted below.
Is FTD hereditary?
In the majority of cases, FTD is not being inherited within the family. However, people with both inherited and sporadic (not inherited) FTD exhibit the same clinical symptoms, which makes evaluation of the family history the most sensitive tool for determining the likelihood of a genetic cause.
While scientists have found gene mutations that are linked to FTD, most cases of FTD are sporadic, meaning that there is no known family history of FTD. Current genetic research shows that if a diagnosed individual has no family history of FTD or related neurological conditions, there is less than a 10% chance that they carry a mutation in a currently known FTD gene.
However, approximately 40% of individuals with FTD do have a family history that includes at least one other relative who also has or had a neurodegenerative disease. In approximately 15-40% of all FTD cases, a genetic cause (e.g., a gene mutation) can be identified as the likely cause of the disease and in most cases it is an inherited mutation.
As seen in the pie chart above, families that include a history of multiple relatives with FTD and/or ALS are the most likely to have an underlying genetic cause (shown in yellow), while cases with sporadic or unknown family histories are the least likely (blue). There are also families that fall in the middle (green), meaning that there is at least one relative who has or had a related neurodegenerative disease like Alzheimer’s or Parkinson’s disease, but not a clear-cut family history of FTD or ALS in close relatives. In short, the greater the family history of FTD or an associated disease like ALS, the more likely genetics plays a role. It is important to note that not all individuals with a family history of neurodegenerative disease will have an identifiable gene mutation. This could be because the responsible gene has not yet been identified, or because the disease is not actually due to a gene mutation.
What should I do if I think FTD may be inherited in my family?
If there is no history of neurodegenerative conditions in your family, it is unlikely that there is a single gene responsible for the disease. However, if your family history does raise some concerns, there are some important steps you can take.
1. Get informed. Read the booklet Understanding the Genetics of FTD: A guide for patients and their families. Talk to the neurologist about your concerns.
2. Talk to other members of your family. Not all relatives will want to pursue this information, so you may need to be sensitive to their wishes. But an important step is to gather as much family history as possible. Ask questions about the early symptoms of any family member affected with FTD or a related disease. Find out the age of onset of symptoms.
3. Ask for a referral to a genetic counselor or other healthcare professional experienced in the genetics of adult neurological conditions. You can find such a professional by asking at your neurologist’s office or by contacting the National Society of Genetic Counselors at www.nsgc.org.
A genetic counselor or geneticist develops a family pedigree, which is a graphic description of family tree with health history, to record information collected from patients and families. Ideally, one should research at least three generations of relatives.
4. Stay calm. You’ve already taken an important first step by gathering information and exploring your options. You can explore the possibility of genetic testing with your genetic counselor or doctor. You can contact AFTD’s HelpLine with questions and be sure to register with AFTD to ensure that you stay informed as new scientific discoveries occur.