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What Is Fuchs' Dystrophy?
Fuchs' Dystrophy (FD) is an eye disorder in which cells of each cornea progressively die. Specifically, FD affects the cells that are present along the rear portion of each cornea. It is an important function of these cells to excrete fluid from the cornea. When these cells die off in large enough numbers, which is typically what occurs in FD sufferers, excess fluid builds up in the corneas and causes them to swell up and become cloudy. In time, other problems arise, such as the emergence of very small blisters (which are known as "guttae") on the corneas, which frequently break and cause discomfort and pain, for example. In the most severe cases, FD causes the corneas to become misshapen, which leads to significant vision troubles. Commonly experienced FD symptoms include:
- Sensitivity to bright light
- Blurry vision
- Decreased vision
- Eye pain
- Appearance of rings around lights
While FD can strike a person of either sex, it affects more women than it does men. The typical onset of symptoms occurs, on average, at about age 50, but FD symptoms sometimes arise in much younger individuals.
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Diagnosis, Treatment And Prognosis
FD is relatively easily to diagnose. Often this is achieved by using a slit-lamp, a high intensity light source that shines light into the eye in such a manner that permits an eye doctor to thoroughly inspect the inside of the eye. Other useful tests include traditional eye tests where one eye is blocked and the individual is asked to read rows of the letters that become progressively smaller and certain techniques that allow an eye doctor to measure the thickness of the cornea and to examine the cells that line its back portion.
The only known way to cure FD is to replace the affected corneas with healthy ones that are removed from deceased organ donors. However, if such transplantation is not an option, FD symptoms can be somewhat alleviated by using eye drops that are designed to drain fluid from the corneas and contact lenses, which not only improves vision, but also soothes any guttae that may be present.
Unfortunately, FD symptoms become worse as time progresses. Therefore, in cases in which cornea transplants are not elected, it is very likely that the affected individual will become blind or nearly blind.
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What Is Known About The Genetics
In many cases, FD is inherited in an autosomal dominant manner from a parent who also suffers from FD (or will eventually suffer from FD). Interestingly, however, there have been instances in which FD strikes individuals who do not have a parent who also has FD. This suggests that FD is not a genetic disorder in some individuals, or it suggests that FD is sometimes genetically inherited in an autosomal recessive manner. Further work will need to be performed to determine the exact cause of FD cases that are not genetically inherited in an autosomal dominant fashion.
The underlying genetic basis of the autosomal dominant form of FD was reported in the summer of 2010. Specifically, a team of U.S. human molecular geneticists discovered that mutations in a gene known as transcription-factor-4 (TCF4) are responsible for causing the autosomal dominant form of FD. The TCF4 gene encodes a protein that regulates the activity of one or more other genes. However, it remains unknown which other gene or genes are affected by the loss of, or reduction in, TCF4 gene activity (due to mutation) in FD individuals, and it also remains unknown how the loss of, or reduction in, activity in this other gene or genes causes the death of the cells that line the back region of the cornea. Efforts toward answering these questions are underway, however, now that the underlying TCF4 gene and its mutations have been identified.
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K.H. Baratz et al., E2-2 And Fuchs' Corneal Dystrophy, The New England Journal of Medicine: http://www.nejm.org/doi/full/10.1056/NEJMoa1007064
Mayo Clinic, Fuchs' dystrophy: http://www.mayoclinic.com/health/fuchs-dystrophy/DS01147
Medline Plus, National Institutes of Health, Fuchs' dystrophy: http://www.nlm.nih.gov/medlineplus/ency/article/007295.htm
National Eye Institute, National Institutes of Health, Facts About The Cornea And Cornea Disease: http://www.nei.nih.gov/health/cornealdisease/index.asp#e
The Corneal Dystrophy Foundation, Fuchs' Dystrophy Home Page: http://www.fuchs-dystrophy.com/