In the last several years considerable evidence has accumulated which argues that Alzheimer’s disease (AD) is etiologically heterogeneous. In particular, molecular genetic studies of pedigrees with familial Alzheimer’s disease (FAD) have provided quite convincing evidence that different primary events (defects in different genes) are capable of causing the same general disease phenotype associated with AD (i.e., adult onset progressive dementia accompanied by the characteristic neuropathologic features of neurofibrillary degeneration and amyloid deposits, etc.). This review will examine some of the molecular genetic evidence for etiologic heterogeneity.
