There are approximately 60 known females worldwide with this rare condition, although it is believed that there are probably many more who are undiagnosed.
More information about pentasomy X or 49,XXXXX:
Physical traitsXXXXX syndrome is associated with microcephaly (undersized skull), micrognathia (undersized jaw), and round face. The ears are generally low-set and malformed. Eyes are upslanting and show palpebral fissures, hypertelorism, and strabismus. Usually the nose is shaped with a broad and depressed nasal bridge and epicanthus, with the mouth having a cleft and highly arched palate, dental abnormalities, and thick, furrowed, and everted lips. The neck is webbed, much like the neck of a woman with Turner's syndrome.
Growth and developmentXXXXX syndrome causes mental, growth, and motor retardation. There is occasional delayed puberty. Recent observations have indicated an average of a 10 to 15 IQ point decrease for each extra X chromosome. Thus, the average IQ of XXXXX individuals tends to be between 55 and 70.