RTT has an X‐linked dominant pattern of inheritance and mainly affects females with an approximate 1:10,000 incidence featuring predominantly de novo mutations in the methyl‐CpG‐binding protein 2 (MECP2) gene (Carter et al., 2010; Corchón, Carrillo‐López, & Cauli, 2018; Leonard et al., 2017). The gene discussed is MECP2; the disease is Rett syndrome.