SNCA and Alzheimer disease: AD and MSA do not share a common brain pathology, however, it is not unusual to observe the co-occurrence of synuclein, amyloid, and/or tau pathology and in fact several studies have focused on the potential role of α-synuclein in the pathophysiology of AD [71] and it has also been reported that α-synuclein inclusions are found in more than 50% of autopsy-confirmed AD cases [4, 32, 42].