In order to explain the differences of Down Syndrome, Turner Syndrome, and Klinefelter Syndrome, it is necessary to state the characteristics of each. These abnormalities share the characteristic of having aneuploid cells, that is, cells that do not contain a multiple of 23 chromosomes. However, Down Syndrome is different from Turner Syndrome and Klinefelter Syndrome because the abnormality results from an autosome that is trisomy; chromosome 21. In other words, the chromosome 21 has three copies.
Down Syndrome is found in both females and males, and while nearly all males are found to be sterile, in some cases females have the capability to reproduce. According to Huether & McCance, the musculoskeletal system of an individual with Down Syndrome has low muscle tone and is short in height. Over one third of these cases have congenital heart disease, a reduced ability to fight respiratory tract infections, increased chances of having leukemia, and have a low survival rate. By the age of 40 there is usually a development of symptoms similar to those found in Alzheimer disease. The mortality rate in Down Syndrome is high, an estimated 75% of fetuses are either stillborn or abort spontaneously. For those that do survive, 20% die near the age of 10 years old, or have a life expectancy of 60 years. The mostfactor in Down Syndrome is nondisjunction during the formation of one of the parent’s gametes during the preliminary stages of the embryo development (Huether & McCance, 2017, p.46).
On the other hand, Turner Syndrome and Klinefelter Syndrome both have a sex chromosome aneuploidy. This means there is not a multiple of 23 chromosomes and the abnormality is found specifically in the sex chromosomes, as opposed to Down Syndrome where the abnormality takes place in autosomes. Distinctively, Turner Syndrome is only found in females. As stated in the read by Huether & McCance, the lack of a homologous X or Y chromosome leaves a total count of only 45 chromosomes instead of the usual 46. The musculoskeletal system in an individual with Turner Syndrome is also shorter than the average height, but it is characterized more by an individual’s webbed neck, reduced carrying angle at the elbow, and widely spaced nipples. Most Turner Syndrome cases are found to be sterile and have gonadal streaks rather than ovaries, which in some cases are susceptible to cancer. Other systemic disorders include coarctation or narrowing of the aorta, and edema of hands/feet in newborns. Mortality rates for Turner Syndrome are lower than Down Syndrome, there is an estimate of 15-20% of spontaneous abortions found with this type of abnormality (Huether & McCance, 2017, p.46). The causative factors for Tuner Syndrome have been found to be a genetic alteration due to a missing X chromosome or only having a partial X chromosome. Although, the exact reason behind this abnormality has not been pointed, it is thought to be a result of an error during formation of eggs or sperm (National Human Genome Research Institute, 2011).
Lastly, Klinefelter Syndrome is unique in that it is identified by individuals with two or more X chromosomes and one Y chromosome. Individuals have male characteristics, and most are sterile. Klinefelter Syndrome is distinguished by sparse body hair, and small testicles. (Huether & McCance, 2017, p.46) Like Down Syndrome, Klinefelter Syndrome cases result because of a nondisjunction of X chromosome in the mother. The chances of nondisjunction increase as the maternal age increases.
I personally do not know anyone with any of the abnormalities described. However, after watching a video of individual with Turner Syndrome I learned that Turner Syndrome girls’ characteristics can vary depending the type of abnormality in the individual’s karyotype. I also learned that a lot of the physical traits can be treated with growth hormones to assist in the delayed growth and the common short stature.