A genetically inherited sex chromosome abnormality only affecting females. Metafemales inherit three X chromosomes--their genotype is XXX. As adults, these individuals are usually an inch or so taller than average with unusually long legs and slender torsos. They have normal development of sexual characteristics and are fertile. They may have slight learning difficulties and are usually in the low range of normal intelligence. They tend to be emotionally immature for their size during childhood. None of these traits prevent them from being socially accepted as ordinary women. This type of chromosomal abnormality is apparently rare and little is known about it. However, the frequency is approximately 1 in 1,000 female infants and it may be more common when the mother is older. Metafemales are also called "triple-X females. "