SNCA and Parkinson disease: When PD begins, the complex features of motor and non-motor symptoms reflect the progression of underlying pathologies, including α-synuclein immunoreactive inclusions in Lewy bodies; loss of dopaminergic, cholinergic, serotonergic, and noradrenergic projections from the brainstem to the midbrain and basal forebrain; and, finally, to the neocortex (5).