STXBP1 and Parkinson disease: First, both in vitro and in vivo studies have shown that STXBP1 is critical for neuronal survival and maintenance.5,6 Furthermore, a recent study revealed that STXBP1 controls the self-replicating aggregation of α-synuclein, a protein involved in various neurodegenerative diseases including Parkinson disease.17 By definition, neurodegenerative disorders deteriorate with age; hence, a study of older patients with STXBP1-DEE provides a unique opportunity to look for clinical signs of neurodegeneration.