In the first longitudinal PET study comparing the tracer binding of [11C]PIB and [18F]FDDNP in AD, mild cognitive impairment (MCI) patients and healthy controls, [18F]FDDNP successfully discriminated between AD and healthy controls yet with a ninefold lower specific binding signal in comparison with [11C]PIB, which was thought to be due to both amyloid and tau [17]. This evidence concerns the gene MAPT and Alzheimer disease.