We genotyped the HTT gene CAG repeat number and APOE‐E isoforms in a cohort of patients with neuropathological diagnoses of tauopathies (n=588), including 34 corticobasal degeneration (CBD), 98 progressive supranuclear palsy (PSP) and 456 Alzheimer's disease (AD). Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.