Primary progressive aphasia (PPA) is caused by damage and loss to brain cells in the front and sides of the brain, called the frontal and temporal lobes. However, the causes for this loss in PPA are not yet clear.

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 early-onset Alzheimer’s.

In rare cases, semantic dementia or primary non-fluent aphasia can be caused by a faulty gene that is passed down in families. The genes involved are called MAPT, progranulin (or GRN) and C9ORF72. 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 here.

What causes a lot of dementia cases is a mixture of factors including age, lifestyle, environment, and genetics. While we cannot change our genetics, a lot of our risk can be modified by our lifestyle choices. Keeping active and eating a healthy balanced diet, as well as looking after our heart health, can help to reduce our risk of developing PPA. Find more about how to reduce your risk of developing dementia here.

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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This information was written in April 2021 and is due for review in April 2023. Please contact us if you would like a version with references.

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