FOXG1 and atypical Rett syndrome: Pathogenic variants in FOXG1 are associated with autosomal dominant Rett syndrome, congenital variant [MIM 613454], which is characterized by normal birth but development of progressive microcephaly, severe hypotonia, midline stereotypic activities typical of classic Rett syndrome, no spoken language, and electroencephalography (EEG) abnormalities.