Turner Syndrome

This syndrome is typically characterized by a 45,X karyotype in females (in about 50% of cases), with the absence of one X chromosome (and therefore absence of a Barr body). The single X chromosome is of maternal origin in about 70% of cases; therefore there is loss of a sex chromosome due to paternal error. Other possible variations include:

• 46,X,i (Xq) in 15% of cases (isochromosome of X);
• 45,X or 46,XX mosaics in 15% of cases;
• 45,X or 46,X,i (Xq) mosaics in about 5%;
• other.

Its incidence is about 1:2000 (less common than Klinefelter's) and it is present in about 1.5% of all conceptions.

Patients present with the following features:

1. short stature (without hormonal treatment, average height is 145cm);
2. ovarian dysgenesis (streak ovary); this is the most common cause of primary amenorrhea;
3. infertility;
4. shield chest with widely-spaced nipples;
5. webbing of the neck postnatally (cystic hygroma in fetal life; seen in ultrasound);
6. low posterior hairline;
7. average intelligence;
8. renal and cardiovascular abnormalities (e.g. coarctation of the aorta).

There is no actual cure for this syndrome but treatments can be done to alleviate some of its symptoms, e.g. growth hormone, estrogen replacement therapy, and reproductive technologies (to get pregnant as they are infertile, donor egg cell is needed).

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• Disorders of the Sex Chromosomes