SNCA and Parkinson disease: For instance, familial forms of parkinsonism due to αsyn pathogenic substitutions (A30P, E46K, H50Q, G51D or A53T) or due to the duplication or triplication of the wild-type (wt) SNCA gene commonly present with additional atypical clinical signs such as hallucinations, cognitive impairment, and dementia [32, 35, 41–47].