Turner syndrome
Turner syndrome has a number of physical and psychological impacts, including short stature, heart defects, neck webbing, delayed or absent puberty, and infertility. The phenotype of Turner syndrome is affected by mosaicism, where cell lines with a single sex chromosome are combined with those with multiple. Around 4050% of cases of Turner syndrome are true "monosomy X" with a 45,X0 karyotype, while the remainder are mosaic for another cell line, most commonly 46,XX, or have other structural abnormalities of the X chromosome. The classic features of Turner syndrome, while distinctive, may be rarer than previously thought; incidental diagnosis, such as in biobank samples or prenatal testing for older mothers, finds many girls and women with few traditional signs of Turner syndrome.