STXBP1 and early-infantile DEE: Pathogenic variants in STXBP1 are associated with a wide range of clinical phenotypes, including global developmental delay (GDD)/intellectual disability (ID), Early Infantile Developmental and Epileptic Encephalopathy (EIEE), developmental epileptic encephalopathy (DEE), infantile epileptic spasms syndrome (IESS), and a clinical spectrum of movement disorders ranging from spastic tetraplegia to tremor, ataxia, and Parkinsonism-like features [2].