Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 57 8 2020 02 15 508 521 Masoud Heidari Department of Animal Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran. Morteza Soleyman-Nejad Ariagene Medical Genetics Laboratory, Qom, Iran. Mohammad Hossein Taskhiri Ariagene Medical Genetics Laboratory, Qom, Iran. AND Department of Molecular Biology, Islamic Azad University of Qom, Qom, Iran. Alireza Isazadeh Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran. Manzar Bolhassan Ariagene Medical Genetics Laboratory, Qom, Iran. Javad Shahpouri Pediatric Clinical Research of Development Center, Qom University of Medical Sciences, Qom, Iran. Mansour Heidari Ariagene Medical Genetics Laboratory, Qom, Iran. AND Department of Molecular Biology, Islamic Azad University of Qom, Qom, Iran. Nahid Sadighi Advanced Diagnostic and Interventional Radiology Research Center (ADIR), Tehran University of Medical Sciences, Tehran, Iran. 2019 08 25 2019 10 31 The Syntaxin Binding Protein 1 (STXBP1) plays an important role in regulating neurotransmitter release and synaptic vesicle fusion through binding to syntaxin-1A (STX1A) and changing its conformation. In this study, we identified a de novo mutation (c.C1162T: p.R388X) in exon 14 of the STXBP1 gene causing an epileptic encephalopathy, early infantile, non-epileptic movement, and unclassified infantile spasms disorders in a 5-year-old boy by whole-exome sequencing. The segregation of this genetic variant was examined in the patient as well as in his parents. We found the R388X in heterozygous state in the proband but not in his parents. This genetic change could be due to de nova mutation or germlinemosaicism. https://acta.tums.ac.ir/index.php/acta/article/view/8047 https://acta.tums.ac.ir/index.php/acta/article/download/8047/5307