We report a 31-year-old woman with ring chromosome 20 syndrome who presented with epilepsy staring from 16 years old and loss of consciousness from 30 years old. Her neurological examinations and psychological testing were normal, without dysmorphic features. No abnormalities were found in neuroimaging. Electroencephalogram recording showed typical non-convulsive status epilepticus associated with alteration of consciousness. Her diagnosis was based on the cytogenetic analysis indicating that her karyotype was 46, XX, r(20)(p13q13.3)[9]/46, XX[21]. She had refractory epilepsy and improved by a combination of valproate and lacosamide.