My sister is 45 and was diagnosed with CMT as a child and is doing well considering her limitations...my question, however, is for my friend whose son was recently diagnosed with CMT also. When doing the blood testing, it showed that neither his mother or father carry the gene....is it possible to get CMT if there is no genetic history involved? My sister's came from my mother's side of the family. When my friend asked the doctors from Columbia University Hopsital in NY, first they said that it HAD to be genetic, and since the parents both tested negative, their answer is that it has to "start somewhere"...I don't find this an acceptable answer. She is in the process of bringing him to the Mayo Clinic at the end of May to have more genetic testing/diagnoses and evaluations done...any input would be greatly appreciated.
As you know, Charcot-Marie-Tooth disease is a group of progressive conditions that affect the peripheral nerves. The different types of CMT can be distinguished by the abnormality that disrupts proper nerve function (what part of the nerve is affected) as well as by their genetic cause. Currently, there are at least four classified types of CMT with over 25 classified subtypes. In addition, the inheritance pattern of CMT disease varies by type and in some cases, by subtype.
In cases of CMT disease that involve autosomal dominant inheritance, a mutation in a single gene copy is sufficient to cause the disease. Many people with autosomal dominant CMT disease have an affected parent; however, some people are the first one in their family with the disorder. In these individuals, their genetic condition is a result of a new, sporadic mutation.
In cases of CMT disease that involve X-linked dominant inheritance, a mutation in a gene on the X chromosome (one of the two sex chromosomes) causes the condition. Although not common, similar to autosomal dominant CMT disease, some individuals are the first one in their family to be affected.
In cases of CMT disease that involve autosomal recessive inheritance, two mutations, one in each gene copy, are necessary to cause the condition. As such, these cases are less likely to be caused by a new mutation and are typically inherited.
We gathered that your friend and her son are meeting with genetics at Mayo for further testing and evaluation. A genetic health professional can provide a more accurate risk assessment based on family history, physical evaluations, and genetic testing results. Hopefully, the results of their son’s testing will help further clarify CMT disease type and subtype and therefore, the inheritance pattern.
We are happy to hear your sister is doing well, and we wish your friend’s family the best.
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