Expanding the Phenotype: Myoclonus–Dystonia as a Novel Manifestation of 47 XXX Syndrome

Triple X Syndrome (TXS), 47,XXX is a sex chromosome aneuploidy resulting from nondisjunction during meiosis, first described by Jacobs in 1959 and has an approximate incidence of 1 in 1000 live born females. (1)The phenotype in this disorder is hypothesised to occur from overexpression of genes that escape X-inactivation, and only about 10% of the cases are diagnosed as it is generally mild. (2)Reported features include developmental delay, intellectual disability,