MAPT and early-onset autosomal dominant Alzheimer disease: The use of CSF (e.g. tau and amyloid-β levels) and neuroimaging biomarkers (e.g. hippocampal atrophy on structural MRI, temporoparietal hypometabolism on FDG PET, abnormal amyloid and tau PET imaging) to make the diagnosis of Alzheimer’s disease in the ‘preclinical’ state is one strategy that has gained widespread currency (Jack and Holtzman, 2013; Ahmed et al., 2014).