MAPT and Alzheimer disease: Globally, more than 55 million people live with dementia, including over 900 000 people within the UK.8 9 Dementia is a clinical syndrome that can be caused by several progressive diseases that damage the brain and destroy nerve cells, which leads to a deterioration in cognitive function and changes in mood and behaviour.8 10 11 The most common form of dementia is Alzheimer’s disease (AD), which accounts for 60–80% of cases and is associated with amyloid and tau pathology within the brain.12