Abstract: AbstractObjective：To explore the clinical features and genetic characteristics of patients with SLC6A1 gene mutations. Methods：The clinical data of a patient with SLC6A1 gene mutation from Children's hospital of Fudan university were collected. The related literatures were searched from Wanfang Data Service Platform, China National Knowledge Infrastructure, National Center for Biotechnology Information and Pubmed (up to June 2017) by using search terms "SLC6A1" and "epilepsy". The clinical features, electroencephalogram and treatment of the patients with SLC6A1 gene mutations were studied. Results：A boy with absence seizures and psychomotor retardation was followed up whose first attack happened at the age of 3 years. The seizures manifested as absence with eyelid flutter, with no limb convulsions and the duration varied from seconds to dozens of seconds. The seizure frequency ranged from once in several weeks to daily cluster seizures. Electroencephalogram was abnormal because of bursts of generalized 3 to 3.5 Hz spikeandwave activity. Whole exomesequencing study (trios) identified a de novo splicing mutation of c.370+1G>T in SLC6A1. It was not previously reported in public database and predicted deleterious by Mutation Taster. And this was the first case of SLC6A1 gene mutation in China. A total of twelve patients including the present case with SLC6A1 gene mutation were studied. Among them, 11 cases had absence seizures, including 5 typical absence and 5 absences with eyelid myoclonias, the other one case was atypical absence. Ten mutations were identified, including 5 missense mutations, 2 truncated mutations, 1 frameshift mutation, 1 splicing mutation and one with chromosome microdeletion.Conclusion：SLC6A1 gene mutation is one of the causes of absence seizures with mental retardation or developmental regression.