Older patients with Munc18-1 mutations also show signs of Parkinsonism including tremor and bradykinesia (Keogh et al., 2015; Álvarez Bravo and Yusta Izquierdo, 2018).Co-aggregation of mutant Munc18-1 with α-synuclein is thought to be the underlying mechanism of parkinsonian symptoms that are seen in older patients (reviewed in Lanoue et al., 2019). This evidence concerns the gene STXBP1 and Parkinsonism.