Approximately 5% of patients develop symptoms before age 65 [early-onset Alzheimer’s disease (EOAD)]5—of these, approximately 5–10% have a dominantly inherited form of Alzheimer’s disease (DIAD, most commonly due to mutations in PSEN1), and the rest have apparently sporadic EOAD (sEOAD6,7).7-9. The gene discussed is PSEN1; the disease is early-onset autosomal dominant Alzheimer disease.