The cause and the phenotypes of 47, XXX syndrome are discussed. XXX syndrome majorly derives from the maternal nondisjunctional errors during meiosis I or II, while 46, XX/47, XXX mosaic are caused by the nondisjunctional errors in zygotic mitosis during early embryonic development. Unlike other sex chromosome aneuploidy, there are no characteristic physical features for triple X patients. They are always female, usually taller than average in height, normal or delayed intelligent development, mostly fertile with no specific medical problems. 47, XXX syndrome is suggested to be associated with various diseases, but no significant evidence has shown the correlation between them. Genetic counseling is usually given to the 47, XXX patients and their parents concerning about the potential developmental and medical risks of this syndrome.
