Is Frontotemporal Dementia Hereditary?

Sometimes. Most cases of frontotemporal dementia (FTD) are not inherited, but FTD runs in families far more often than most other types of dementia. Estimates vary: Alzheimer's Society puts the share of FTD caused by a single faulty gene passed down in families at about 10 to 15 in every 100 people, and research reviews estimate 10 to 30%. That compares with under 1% of Alzheimer's disease.

Many more people with FTD, around 4 in 10, have some family history of dementia or a related brain condition, even when no single gene is found.

This page covers FTD specifically. For dementia in general, see is dementia hereditary?

The three main genes

Most inherited FTD is caused by changes in one of three genes:

Changes in other genes, such as TBK1, are rarer. In some families with a clear pattern of FTD, no gene has yet been found.

Genetic FTD most often causes behavioural variant FTD, and is less often linked to the language-led types (primary progressive aphasia). People whose FTD is caused by a single gene are also more likely to develop MND.

How it is passed on

These genes are inherited in an autosomal dominant way. That means:

• Each child of a person with genetic FTD has a 1 in 2 (50%) chance of inheriting the faulty gene.
• Men and women are equally likely to inherit it and to pass it on.
• A child who does not inherit the gene cannot pass it on to their own children.

Inheriting the gene does not always mean developing FTD, and it does not decide exactly when or how symptoms will appear. This varies by gene, and even within the same family.

Signs that FTD may be genetic

FTD is more likely to be inherited if:

• Several relatives across more than one generation have had FTD, MND, or dementia that started before 65
• A parent or sibling had FTD, especially behavioural variant FTD
• Symptoms started at a younger age
• A relative has already been found to carry an FTD gene

Families sometimes don't know the full history, because relatives may have been given other diagnoses in the past, such as early Alzheimer's disease, a psychiatric illness or Parkinson's disease.

Genetic testing

There are two kinds of genetic testing for FTD:

• Diagnostic testing for someone who already has symptoms, to find out whether a gene change is the cause. In the UK this can be arranged through specialist neurology and genetics services. Many specialists now suggest considering it for anyone diagnosed with FTD, not only those with a family history.
• Predictive testing for healthy relatives of someone with a known FTD gene change, to find out whether they have inherited it. This is a major personal decision, because there is currently no treatment that prevents FTD. It is offered through clinical genetics services, with genetic counselling before and after the test to help people think through what a result would mean for them, their families, work, insurance and future plans.

Some families choose to take part in research studies that follow gene carriers over many years. These studies are helping researchers understand the earliest changes in genetic FTD, and they are the basis for clinical trials of treatments aimed at specific genes.

What if FTD isn't genetic?

For most people with FTD, no single inherited cause is found. These cases are called sporadic. If you are worried about your family history, your GP can refer you to a genetics service, which can look at your family tree and explain what it means for you.

Related pages

• 7 stages of frontotemporal dementia
• Frontotemporal dementia vs Alzheimer's
• Is dementia hereditary?