Dementia has been the UK’s leading cause of mortality over the last decade, affecting nearly one million individuals, with Alzheimer's disease (AD) representing the majority.1 AD is characterised by the presence of amyloid (A) plaques, aggregation of intraneuronal tau (T) tangles and neurodegeneration (N) (ATN signature).2 AD for many individuals has a long preclinical phase, with asymptomatic ATN changes developing over up to two decades,2 yet most AD is identified only in the late symptomatic phase. The gene discussed is MAPT; the disease is Alzheimer disease.