MECP2 duplication syndrome (MDS) is a rare and severe neurodevelopmental disorder frequently associated with epilepsy. Different seizure types and electroencephalographic (EEG) patterns were described in patients with MDS, although it lacks a specific phenotype. We report on an adult patient with long-term epilepsy showing an evolution of the EEG pattern that progressively changed into burst suppression (BS) during sleep. As BS has not been previously reported in MDS, this report expands the neurophysiological phenotype of MDS and further suggest the possible occurrence of a longitudinal spectrum of seizure types and EEG patterns in MDS.