FTD: The Other Side of ALS 

When people hear “ALS,” they often think of Lou Gehrig, ice bucket challenges, and the devastating loss of motor function that characterizes Amyotrophic Lateral Sclerosis. But there is another side to ALS that is lesser known, equally devastating, and deeply connected: Frontotemporal Degeneration (FTD). 

FTD and ALS are closely related disorders that are part of the same underlying proteins that damage nerve cells. While ALS attacks the body, FTD disorders attack the mind, changing personality, behavior, language, and decision-making. In fact, up to 50% of people diagnosed with ALS will experience some cognitive or behavioral changes, and about 15% will meet the full criteria for a diagnosis of FTD-ALS. The reverse is also true: about 20-30% of people diagnosed with an FTD disorder will later develop motor symptoms consistent with ALS.  

Two Disorders, One Root 

FTD and ALS share overlapping genetic causes and pathological markers, which are signs in the body that something is going wrong. In fact, when both FTD and ALS are present in the same family, or same person, there is a strong likelihood there is a genetic cause. The C9orf72 gene is the leading genetic cause for both FTD and ALS. This gene normally contains a short sequence that repeats a few times, which is harmless, but when the number of repeats becomes too large (called an expansion), it can cause either FTD, ALS, or both. This expansion leads to a build up of a protein called TDP-43 in the brain or spinal cord.  This protein is found in nearly all people with ALS, whether or not there is a genetic change.  In those diagnosed with FTD, TDP-43 is seen in nearly half of those diagnosed. Based on a number of shared genetic causes (including C9orf72) and similar proteins (TDP-43), research now places FTD and ALS on a disease spectrum. In other words, they are part of the same underlying process, but show up differently depending on which part of the brain or nervous system is affected first. Even when there is no family history of FTD or ALS, the same protein, TDP-43, can underlie both disorders.  

In ALS, motor neurons degenerate, leading to muscle weakness, paralysis, and eventually loss of speech and the ability to breathe. In FTD disorders, neurons in the frontal and temporal lobes of the brain degenerate, leading to changes in  cognition, language, or movement.  

The Role of Genetic Testing and Counseling 

Because of the strong genetic link between FTD and ALS—particularly involving C9orf72, but also with VCP, TBK1, TARDBP, and many other genes. Genetic testing is a vital tool for understanding risk, especially in families where more than one person has been affected. 

But genetic testing should not be undertaken casually. Genetic counseling plays a critical role in ensuring people understand the benefits, risks, and limitations involved in genetic testing. A trained genetic counselor can help families: 

• Understand if testing is appropriate 

• Discuss the social, legal, and practical considerations of testing 

• Prepare for the psychological and family implications of knowing one’s genetic status 

• Navigate next steps for care or participation in clinical research 

Genetic information not only helps individuals and families plan, it also plays a vital role in shaping the future of treatment, especially as research increasingly targets the underlying genetic causes. 

Numbers Have Power: The FTD Disorders Registry 

One of the most powerful ways to contribute to progress is by joining the FTD Disorders Registry. This secure, patient-driven portal provides information on clinical trials and other research opportunities. The Registry also runs its own research study to learn more about the experience of persons diagnosed, biological family members, and care partners.  

By enrolling, you can: 

• Help researchers understand the full picture of FTD and its many forms 

• Learn about and be invited to participate in clinical trials and studies 

• Contribute your voice as someone with lived experience 

• Accelerate the search for treatments and, eventually, a cure 

You do not need to have genetic testing or a diagnosis to make a difference. Anyone with an interest in FTD disorders research is welcome to join the Registry. 

Why Awareness and Action Matter 

FTD disorders are still vastly underrecognized. Most people have never heard of them. This is further compounded by the fact that clinical care is different between those facing ALS versus FTD. Thus, a person receiving care for FTD may not be aware of the risk for ALS, and vice versa. By raising awareness, encouraging genetic counseling, breaking down the silos of clinical care, and participating in research, we can build a community of informed patients, care partners, and providers. This helps ensure that early symptoms are not missed for either condition. 

FTD and ALS are underdiagnosed, misunderstood, and underfunded. But that is beginning to change because families, advocates, researchers, and people living with these disorders are speaking up and joining together. 

Moving Toward Hope 

The research landscape is evolving rapidly. Collaboration between FTD and ALS researchers is growing. New therapies are in development, especially those targeting the underlying genetic causes. Biomarker research is accelerating. A few basket trials have started; these include people with both FTD and ALS. And community-driven efforts like the FTD Disorders Registry are helping scientists access the real-world data they need. 

FTD and ALS may manifest differently, but they share biology, burden, and hope. Recognizing the connection between them is not just medically accurate; it is essential to building a future where no family has to face these disorders alone. 

You Are Not Alone: Contact the AFTD HelpLine 

Navigating an FTD or ALS diagnosis can feel overwhelming, but help is available. The Association for Frontotemporal Degeneration (AFTD) offers information, resources, and guidance to patients, care partners, and medical professionals. If you have questions about symptoms, diagnosis, or support services, reach out to the AFTD HelpLine at 1-866-507-7222 or via email at info@theaftd.org. 

Compassionate professionals are available to listen, guide, and support you, no matter where you are on the journey.