Although new and more specific PET radiotracers (e.g., amyloid and tau) have been introduced, 18F-FDG PET remains widely used for diverse purposes, such as for evaluating brain tumor malignancy, for localizing epileptic zones, for diagnosing dementia and Parkinson disease differentially, and for staging Alzheimer disease (7–10). The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.