Turner syndrome results from the absence, partial or complete, of one of the two X chromosomes. Approximately one in 2,500 women is affected by Turner syndrome. There are three forms of Turner syndrome. In the majority of cases (55%), the X chromosome is absent. This is called monosomy X.In 25% of cases, the chromosome is only altered. Finally, in the remaining 20%, the chromosome is present only in certain cells of the body. This is called mosaic Turner syndrome. Since each human being possesses 46 chromosomes, two of which are sexual, the karyotype is 46 XY for men and 46 XX for women. In the case of Turner syndrome, the karyotype is written as 45 X0 or 45 X.SYMPTOMSTurner's syndrome usually results in a small size during childhood, about 20 cm below average, as well as an absence of puberty and menstruation. Other clinical signs may also occur:- infertility in nearly 99% of cases (due to underdeveloped ovaries)-Irregular menstruation or lack of monthly periods - early hypertension- kidney damage- swelling of the hands, feet or back- webbed neck- heart defects- increased risk of diabetes- increased risk of ENT problems (recurrent ear infections, hearing loss)- increased risk of cancerCAUSETurner syndrome is not an inherited disease. It usually results from a genetic abnormality during fertilization. It is not associated with the mother's age. TREATMENTThe treatment of Turner syndrome evolves with age and has to be closely monitored. Growth hormones can be administered during childhood. In adolescence, an estrogen-based treatment, which is normally produced by the ovaries, must be followed to trigger puberty. Finally, in adulthood progesterone will need to be taken, causing monthly periods to start, until around the age of 50.LIFE EXPECTANCYTurner syndrome is not a deadly condition. However, it can still decrease the life expectancy of those affected. This is reduced from about 6 to 13 years compared to that of a healthy person.