Re: Is Turnerīs syndrome inheritable?

Dear Eva,

Thank you for your great question! Turner's syndrome encompasses a number of different phenotypes that can have different causes, but in general refers to females that have a 45, X karotype. This means that they have the normal complement of autosomes but have only one complete X chromosome. There may be a complete absence of the second X chromosome or a partial fragment may persist. Affected individuals develop as females but have a number of disturbances in normal development, including short stature, short neck, and ovarian failure. With respect to the development of the ovaries in Turner's syndrome patients, they develop and differentiate normally but undergo a premature and accelerated loss of germ cells, or oocytes. In normal 46, XX females, oocyte loss begins very early in life (actually before birth) and continues gradually over 30 to 50 years until the onset of menopause. In Turner's patients, germ cell loss is often nearly complete by the first few months or years of life, and is accompanied by fibrosis, or scarring, of the ovarian stromal tissue (the supporting tissue for the oocytes), leading to the formation of "streak gonads".

For the most part, affected individuals have a complete loss of ovarian function, though some patients do retain some residual function. However, these patients are generally infertile and have few if any healthy oocytes at child-bearing age. One method that has been proposed in the medical literature (though I am not sure if it is actually utilized) is to cryopreserve unfertilized oocytes from Turner's syndrome patients when they are very young before oocyte loss is complete, thus increasing the likelihood that a healthy oocyte can be obtained. In theory this approach would probably be most effective in women who are mosaic-meaning that they have a combination of cells in their ovaries, some of which have the normal complement of chromosomes (46, XX) and some which have an abnormal complement (45, X). Although extremely rare, pregnancy in Turner's syndrome patients has been reported and in fact, is more common in individuals with mosaicism. The sources I consulted stated that the rare offspring of these women are likely not at an increased risk for chromosomal abnormalities, including Turner's syndrome. However, a thorough genetic analysis by amniocentesis or other methods is probably warranted.

Though most Turner's syndrome patients are not able to conceive without some sort of intervention, there are several other options. These individuals may be able to have children by in vitro fertilization with a donor egg, ovum transfer, embryo transfer, or they may be able to adopt children.

Unfortunately, very little is known about what might cause the chromosomal abnormalities that lead to Turner's syndrome. There is some evidence to suggest an association with increased paternal age. Other factors, such as seasonal incidence, birth order, sibling sex, and maternal age do not seem to play a role. The possible contribution of environmental factors, such as maternal or paternal drug abuse or ethanol consumption has not been examined.

I hope this information is helpful! There are a lot of Web resources for Turner's syndrome. I have listed a few below.

The University of Maryland, drkoop.com: Turner's syndrome

The Turner's Syndrome Society of Canada

The Turner's Syndrome Society of the United States

-Nikki
nmdavis@fas.harvard.edu