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Turner syndrome (TS), commonly known as 45,X, or 45,XO, [note 1] is a chromosomal disorder in which cells have only one X chromosome or are partially missing an X chromosome (sex chromosome monosomy) leading to the complete or partial deletion of the pseudoautosomal regions (PAR1, PAR2) in the affected X chromosome.
Trisomy X, also known as triple X syndrome and characterized by the karyotype [note 1] 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 females, but is rarely diagnosed; fewer than 10% of those with the condition know they have it.
The syndrome is defined by the presence of at least one extra X chromosome in addition to a Y chromosome, yielding a total of 47 or more chromosomes rather than the usual 46. Klinefelter syndrome occurs randomly. The extra X chromosome comes from the father and mother nearly equally.
Turner syndrome, also known as 45,X or 45,X0, is a chromosomal abnormality characterised by a partial or completely missing second X chromosome, [4] [24] [25] giving a chromosomal count of 45, instead of the typical count of 46 chromosomes.
When the chromosome's structure is altered, this can take several forms: [16] Deletions: A portion of the chromosome is missing or has been deleted. Known disorders in humans include Wolf–Hirschhorn syndrome, which is caused by partial deletion of the short arm of chromosome 4; and Jacobsen syndrome, also called the terminal 11q deletion ...
46, XX male syndrome, also known as de la Chapelle syndrome In this list, the karyotype is summarized by the number of chromosomes, followed by the sex chromosomes present in each cell. (In the second and third cases the karyotype varies from cell to cell, while in the last three cases, the genotype is normal but the phenotype is not.)
This includes patients with Turner Syndrome (45,X or 45,X0) and Klinefelter Syndrome (47,XXY) even though they do not generally present with atypical genitals. XX, Sex reversal : consist of two groups of patients with male phenotypes, the first with translocated Sex-determining region Y protein (SRY) and the second with no SRY gene.
When additional X and/or Y chromosomes are present in 48,XXXY, 48,XXYY, or 49,XXXXY, developmental delays and cognitive difficulties can be more severe and mild intellectual disability may be present. Klinefelter syndrome can also result from an extra X chromosome in only some of the body's cells. These cases are called mosaic 46,XY/47,XXY ...