The are many hypotheses regarding the primary cause of AD, including cholinergic neuron damage, the accumulation of proteins such as amyloid-β (Aβ) in plaques, hyperphosphorylated-tau in neurofibrillary tangles leading to massive loss of synapses, inflammation, the role of butyrylcholinesterase (BChE) in forming Aβ plaques, and oxidative stress. This evidence concerns the gene BCHE and Alzheimer disease.