In patients with PD and chronic constipation, submucosal colonic neurons downregulate vasoactive intestinal peptide (VIP) without neuronal loss, suggesting that constipation may arise from dysfunction rather than depletion of VIP‐ergic secretomotor neurons (Chalazonitis and Rao 2018; Giancola et al. 2017). The gene discussed is VIP; the disease is Parkinson disease.