Importantly, however, significant tracer retention on amyloid PET combined with cerebrospinal fluid findings (reduced amyloid beta-42 and elevated total tau/phospho-tau) may point toward primary Alzheimer's disease (AD) pathology, which is exclusionary to CBD/CBS and PSP diagnoses (3, 15). The gene discussed is MAPT; the disease is early-onset autosomal dominant Alzheimer disease.