Moreover, postmortem and multi-modal imaging studies support the hypothesis that there is a subgroup of patients with PD who could manifest initial α-synuclein pathology in the gastrointestinal tract, namely in the enteric nervous system, with subsequent propagation to the dorsal motor nucleus of the vagus, sympathetic nervous system, brainstem, and the rest of the central nervous system (the so-called ‘body-first’ PD subtype) (Horsager et al., 2020; Borghammer et al., 2022). Here, SNCA is linked to Parkinson disease.