When a family member receives a frontotemporal dementia diagnosis, one of the first questions that comes to mind is: “Will I develop this condition too?”
This concern weighs heavily on families as they watch their loved one experience changes in personality, behavior, and language abilities.
Frontotemporal dementia (FTD) affects the frontal and temporal lobes of the brain, causing progressive deterioration in these critical areas.
The question of whether FTD is hereditary does not have a simple yes or no answer. Understanding the genetic factors behind FTD can help families make informed decisions about their health and future.
Three Types of FTD: Understanding Your Risk
Medical experts classify FTD into three distinct categories based on family history and genetic factors. Each type carries different implications for family members and their risk of developing the condition.
Sporadic FTD
Sporadic FTD represents the most common form, affecting approximately 60% of all cases [1]. People with sporadic FTD have no known family history of the disease. The exact cause remains unknown, making it difficult to predict who will develop this form.
Familial FTD
About 40% of individuals with FTD have a family history of the condition or related disorders like amyotrophic lateral sclerosis (ALS) [1]. This pattern suggests a hereditary component, though not all familial cases have an identifiable genetic cause.
Genetic FTD
Genetic FTD represents a subset of familial cases caused by specific gene mutations. Research shows that 10-20% of all FTD cases fall into this category [2]. These cases follow clear inheritance patterns that can be tracked through genetic testing.
The Genes Behind FTD: What Science Has Discovered
Scientists have identified multiple genes that can cause FTD. Three primary genes account for the majority of genetic cases: C9orf72, MAPT, and GRN. Understanding these genes helps families assess their risk and make informed decisions about genetic testing.
| Gene | Associated Conditions | Key Characteristics | Inheritance Pattern |
|---|---|---|---|
| C9orf72 | FTD, ALS, or combination | Most common genetic cause of both FTD and ALS | Autosomal dominant |
| MAPT | Behavioral variant FTD | Strong family history pattern; does not cause ALS | Autosomal dominant |
| GRN | FTD, Primary Progressive Aphasia | Can affect language and movement; rarely causes ALS | Autosomal dominant |
Additional Genetic Factors
Research has identified several other genes linked to FTD, including TARDBP, VCP, CHMP2B, SQSTM1, UBQLN2, and TBK1 [2]. These genes are less common but still important for comprehensive genetic testing. Recent studies suggest that approximately 50 genes have been confirmed or suspected to influence FTD risk [3].
How FTD Passes Through Families
Genetic FTD follows an autosomal dominant inheritance pattern. This scientific term means that only one copy of a mutated gene from either parent can cause the disease. Each child of someone with an FTD-causing gene mutation has a 50% chance of inheriting that mutation [2].
Understanding Penetrance
Not everyone who inherits a gene mutation will develop FTD. This phenomenon is called reduced penetrance. However, most FTD-causing genes show high penetrance, meaning nearly everyone with the mutation will develop symptoms if they live to their 80s [2].
Age of Onset
FTD symptoms typically begin between ages 50-60, though the range spans from the 30s to the 70s [2]. The specific gene involved often influences when symptoms first appear. Family members can use this information to understand their potential timeline for symptom development.
Genetic Counseling: Your First Step
The Association for Frontotemporal Degeneration (AFTD) strongly recommends genetic counseling as the essential first step for anyone considering genetic testing [4]. This professional guidance helps families understand their options and prepare for the emotional impact of genetic information.
What Genetic Counselors Provide
Genetic counselors offer specialized expertise in several key areas. They help you understand your personal and family history of FTD. They assess your risk of developing the disease based on current scientific knowledge.
Counselors also discuss the benefits and risks of genetic testing. They prepare you for the emotional and psychological impact of test results, regardless of the outcome.
Types of Genetic Testing
Genetic testing for FTD represents a personal decision with significant implications for you and your family. Understanding the two main types helps you make an informed choice.
Diagnostic Testing
Diagnostic testing serves individuals who already show FTD symptoms. This testing can confirm the diagnosis and provide valuable information for treatment planning. It also offers insights that may benefit extended family members.
Predictive Testing
Predictive testing applies to individuals with a family history of FTD who do not yet show symptoms. This testing determines whether someone has inherited a gene mutation. The decision to pursue predictive testing requires careful consideration due to its emotional, psychological, and legal implications.
The Testing Process
The actual genetic testing process is straightforward, typically requiring only a saliva or blood sample. Many laboratories provide home collection kits with pre-paid shipping. However, the results can be complex and have lasting impacts on your entire family.
Making Informed Decisions About Your Future
Frontotemporal dementia can be hereditary, but the picture is more complex than a simple yes or no answer. While most cases are sporadic, a significant portion have genetic components that families can identify and understand.
If you have a family history of FTD or related conditions, knowledge about genetic factors empowers you to make informed decisions. Genetic counseling provides the professional guidance needed to understand your risk and explore your options.
The decision to pursue genetic testing is deeply personal and affects not just you, but your entire family. With proper support and information, families can face these decisions with confidence and clarity.
References
[1] The Association for Frontotemporal Degeneration. (n.d.). FTD & Genetics Overview. Retrieved from https://www.theaftd.org/what-is-ftd/genetics-overview/
[2] University of California, San Francisco Memory and Aging Center. (n.d.). Familial FTD. Retrieved from https://memory.ucsf.edu/genetics/familial-ftd
[3] Sirkis, D. W., Geier, E. G., Bonham, L. W., Karch, C. M., & Yokoyama, J. S. (2019). Recent advances in the genetics of frontotemporal dementia. Current Genetic Medicine Reports, 7(1), 41-52. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC6827567/
[4] The Association for Frontotemporal Degeneration. (2020, November 2). The Genetic Testing Process. Retrieved from https://www.theaftd.org/ftd-genetics/genetics-testing/
