History/Causes
Types of CMT
Genetics
Diagnosis/Prognosis
Treatment
Living With CMT
New Research
Interesting Tid-Bits
Interview of Child With CMT and his Family
References
CMT is a hereditary disease, meaning that it is passed to the children of carriers through their genes. There are three ways in which this disorder can be passed down to subsequent generations: autosomal dominant, autosomal recessive, and through the X-linked chromosome. When the disease is autosomal dominant, only one of the mutated genes is needed, while with an autosomal recessive form of the disease two copies of the mutated gene are needed for the disease to develop. In the X-linked form of the disease the mutated or abnormal gene needs to be present on the X chromosome for the disease to be passed on. The manner in which the disease is passed on will determine which type of CMT the person may develop.(2,3,6) Due to the results of the research that has already been done, genetic testing has been developed for the phenotypes of CMT. There have also been developments in diagnostic blood tests for CMT 1A and 1B, HNPP, x-linked CMT, as well as prenatal tests for CMT 1A. The ability to perform these tests is helpful so that the specific type of the disease can be determined.(7)
While for the most part, CMT is diagnosed once the child is already born and has the disease, there are different tests available to determine if you are a carrier of the disease or if you have passed those genes on to your unborn child. It is possible in some cases to have a pregnancy without CMT other than the 50/50 chance if you just "wing it." This is not science fiction. We refer to this testing as preimplantation genetic diagnosis (PGD). [] PGD is performed by going through in-vitro fertilization (IVF), and when the embryo is at the 6-8 cell stage, a single cell is removed for genetic testing.(6) Genetic testing can also be performed once the woman is already pregnant through amniocentesis.(6)
Part of the decision making process about whether or not to have genetic testing includes the ethical aspect. First, should the parents find out if their child could develop the disease or not? Second, if they find out that the child is a carrier and could develop CMT do they want to continue on with the pregnancy, or in the case of PGD, have the child implanted into the womans uterus regardless of the outcome. Thirdly, once the parents know their child is a carrier for CMT, do they do genetic tests on themselves to see which one of them passed the mutated gene on. These are all aspects that the couple needs to consider before undergoing genetic testing.
References
1Maxwell B. CMT2A A New Gene. Hereditary Neuropathy Foundation. 2004. Available at: http://www.hnf-cure.org/epublisher/publish/article_00143.php. Accessed February 16, 2005.
2Charcot-Marie-Tooth Disease Fact Sheet. National Institute of Neurological Disorders and Stroke. 2003. Available at: http://www.ninds.nih.gov/disorders/charcot_marie_tooth/detail_charcot_marie_tooth.htm#What%20causes%20Charcot-Marie-Tooth%20disease?. Accessed February 20, 2005
3Passing Genes to Our Children. Hereditary Neuropathy Foundation. 2004. Available at: http://www.hnf-cure.org/news/fullnews.php?id=80. Accessed February 16, 2005.
4Donahue G. Facts About Charcot-Marie-Tooth Disease and Dejerine Sottas Disease. MDA Publications page. 2002. Available at: http://www.mdausa.org/publications/fa-cmt.html#causes. Accessed March 1, 2005.
5Heat Shock Proteins. Hereditary Neuropathy Foundation. 2004. Available at: http://www.hnf-cure.org/epublisher/publish/article_00137.php. Accessed March 12, 2005.
6CMT and Pregnancy. Hereditary Neuropathy Foundation. 2004. Available at: http://www.hnf-cure.org/epublisher/publish/article_0046.php. Accessed March 9, 2005.
7Research History. Charcot-Marie-Tooth Association. Available at: http://www.charcot-marie-tooth.org/site/content/research/index.asp Accessed March 28, 2005.