Turner syndrome
45,X
Also known as: Monosomy X, 45 X
45,X is the karyotype of Turner syndrome, in which a single X is present and the second sex chromosome is missing. Short stature and ovarian insufficiency are characteristic, and loss of the SHOX gene drives much of the growth phenotype.
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What the notation means
45count,Xsex chromosomes
- count
- total chromosome count (normal = 46)
- sex chromosomes
- sex chromosomes: a single X (monosomy X)
Clinical notes
Turner syndrome (45,X and variants)
Loss of all or part of the second sex chromosome. 45,X (monosomy X) is classic; variants include an isochromosome i(Xq), a ring r(X), an SRY-negative rearranged Y, and 45,X mosaicism (e.g. 45,X/46,XX, or with an unstable idic(Y) line). Short stature, ovarian dysgenesis/streak gonads, webbed neck, coarctation/bicuspid aortic valve, lymphedema.