Cerebrospinal fluid (CSF) levels of amyloid beta peptides (Aβ) and Tau proteins have shown good accuracy in distinguishing early Alzheimer's disease (AD) from healthy elderly controls [1], but studies from dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) are scarce. The gene discussed is APP; the disease is early-onset autosomal dominant Alzheimer disease.