Cognitive impairment and dementia are the most disabling non-motor symptoms of PD, resulting from microvascular disease (Kim J.S. et al., 2014), deposition of Lewy bodies in neocortical and limbic areas, hyperphosphorylated tau-containing neurofibrillary tangles and formation of amyloid-beta-peptide plaques (Irwin et al., 2013). The gene discussed is MAPT; the disease is Parkinson disease.