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Turner syndrome (TS), commonly known as 45,X, or 45,X0, [note 1] is a chromosomal disorder in which female cells have only one X chromosome instead of two, 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.
It is the most common autosomal trisomy leading to miscarriage, and the second most common chromosomal cause (closely following X-chromosome monosomy). [2] About 6% of miscarriages have trisomy 16. [3] Those mostly occur between 8 and 15 weeks after the last menstrual period. [3]
Miscarriage is the most common complication of early pregnancy. [19] Among women who know they are pregnant, the miscarriage rate is roughly 10% to 20%, while rates among all fertilisation is around 30% to 50%. [1] [7] In those under the age of 35, the risk is about 10% while in those over the age of 40, the risk is about 45%. [1]
Turner syndrome, monosomy 45XO, is a genetic disorder characterized by a missing, or partially missing, X chromosome. [18] Turner syndrome is associated with a wide spectrum of features that vary with each case. [18] However, one common feature of this syndrome is ovarian insufficiency due to gonadal dysgenesis.
[citation needed] An example of trisomy in humans is Down syndrome, which is a developmental disorder caused by an extra copy of chromosome 21; the disorder is therefore also called "trisomy 21". [7] An example of monosomy in humans is Turner syndrome, where the individual is born with only one sex chromosome, an X. [8]
The most common abnormality the test can screen is trisomy 21 (Down syndrome).In addition to Down syndrome, the triple and quadruple screens assess risk for fetal trisomy 18 also known as Edwards syndrome, open neural tube defects, and may also detect an increased risk of Turner syndrome, triploidy, trisomy 16 mosaicism, fetal death, Smith–Lemli–Opitz syndrome, and steroid sulfatase ...
Complete trisomy 8 causes severe abnormalities in the developing fetus and can be a cause of miscarriage. [2] [3] Complete trisomy 8 is usually a gestational lethal condition, whereas trisomy 8 mosaicism is less severe and individuals with a low proportion of affected cells may exhibit a comparatively mild range of physical abnormalities and developmental delay. [4]
The first described case of pure gonadal dysgenesis was in 1960, in a patient with presumed Turner syndrome but without the expected stigmata. [50] In 1951, Perrault, Klotz, and Housset reported the association of gonadal dysgenesis and deafness in two sisters, and this presentation is now called Perrault syndrome .