49,XXXXX syndrome.

A 3-year-old 49,XXXXX girl, the seventeenth case in medical literature, is described. A typical characteristic of the syndrome is the round face with epicanthal folds, hypertelorism, broad flat nasal bridge, upward slant of the palpebral fissures, enlarged round mandible and pointed chin, somewhat resembling trisomy 21. The apparent stronger selection against 49,XXXXX aneuploidy versus the 49,XXXXY suggested by the much higher frequency of the latter is probably due to the more severe congenital cardiopathy which may be related to the number of inactivated X chromosomes.