Mutation is a Low-Incidence Genetic Cause in Atypical Rett Syndrome.

Due to the genetic and clinical heterogeneity of Rett syndrome, patients with nonclassic phenotypes are classified as an atypical Rett syndrome, that is, preserved speech variant, early seizure variant, and congenital variant. Respectively, , , and have been found to be the causative genes, but variants are the rarest and least studied. We performed mutational analyses for on 11 unrelated patients without and mutations, who were diagnosed with atypical Rett syndrome. One patient, who suffered from severe early-onset mental retardation and multiple-type intractable seizures, carried a novel, de novo mutation (p.Gln70Pro). This case concurs with previous studies that have reported yields of ∼10%. -related atypical Rett syndrome is rare in Korean population, but screening of this gene in patients with severe mental retardation, microcephaly, and early-onset multiple seizure types without specific genetic causes can help broaden the phenotypic spectrum of the distinct -related syndrome.