DDX3X and atypical Rett syndrome: Furthermore, in a 6-year-old girl manifesting a phenotype resembling atypical Rett syndrome (including bruxism, lack of speech, focal epilepsy since the age of 2 years, severe motor delay, stereotypies, and no hand apraxia), we identified a novel frameshift de novo variant in the DDX3X gene: c.1658_1661del, p.(Thr553Argfs*18).