Similarly, for patient 2, it is highly unlikely that the diagnosis of Alzheimer's disease was incorrect: the ApoE4-positive genotype, the FDG-PET scan typical of Alzheimer's disease with temporoparietal reduction in glucose utilization, the pattern and severity of quantitative neuropsychological abnormalities, and the well documented progressive nature of the deficits all provide strong support for the diagnosis of Alzheimer's disease. Here, APOE is linked to early-onset autosomal dominant Alzheimer disease.