Rett syndrome (RTT) is a neurodevelopmental disorder which is mainly caused by pathogenic variants in MECP2. Whole exome sequencing of 77 patients (including typical, atypical RTT and RTT-like) without MECP2 variants achieved positive pathogenic variants in 61.0% of cases (single nucleotide variants; 50.6% and copy number variations; 10.4%). Moreover, we provided possible pathogenic variants in four novel genes (MAST3, ATP6V0A1, USP8, and NCOR2). These findings contribute to a more comprehensive understanding of genetic landscape in RTT-like phenotypes. (By Dr. Kazuhiro Iwama, https://jmg.bmj.com/content/early/2019/03/06/jmedgenet-2018-105775 )