However, the vast majority of RTT patients have a de novo mutation in MECP2, and there are 8 mutation hotpots with recurrent mutations (p.Thr158Met, p.Arg255*, p.Arg168*, p.Arg306Cys, p.Arg294*, p.Arg270*, p.Arg133Cys and p.Arg106Trp), which are responsible for over 60% of all RTT cases9,10. This evidence concerns the gene MECP2 and Rett syndrome.