We know that there is an unusual build-up of certain proteins inside brain cells. These proteins include TDP-43 and tau, and researchers are working hard to find out why this happens and how it damages brain cells.

Different types of PPA often have different protein changes in the brain. Semantic dementia is mainly caused by protein TDP-43, while progressive non-fluent aphasia is most often caused by protein tau. Most cases of logopenic aphasia are caused by the same underlying processes involved in Alzheimer’s disease. This includes the build-up of a protein called amyloid in the brain, which damages brain cells over time. Therefore, logopenic aphasia is often called an unusual or “atypical” form of young onset Alzheimer’s.

In rare cases, semantic dementia or progressive non-fluent aphasia can be caused by a faulty gene that is passed down in families. The main genes involved are called MAPTprogranulin (or GRN) and C9ORF72. These genes are also associated with other forms of dementia. In these cases there is a strong history of family members being affected at a similar age. These genes are also associated with other forms of frontotemporal dementia. Find out more about genes and dementia.

Most cases of dementia are caused by a mixture of factors including age, genetics, lifestyle, and environment. We cannot change our age or genes. However, we can control some lifestyle factors that increase our risk of dementia.  Keeping socially connected, learning a new skill and regularly challenging your brain may help delay or reduce the impact of dementia, though they have not been shown to reduce the risk of PPA specifically. Find more about how to reduce your risk of developing dementia.

What is primary progressive aphasia?

Information in this booklet is for anyone who wants to know more about primary progressive aphasia (PPA). This includes people living with PPA, their carers, families and friends.

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Alzheimer’s Research UK has a wide range of information about dementia. Order booklets or download them from our online form.

This information was written in April 2023 and is due for review in April 2025. It was written by Alzheimer’s Research UK’s Information Services team in association with Rare Dementia Support, with input from expert and lay reviewers. Please contact us if you would like a version with references.

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