Genetics/Inheritance of CMT review

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http://ghr.nlm.nih.gov/condition/charcot-marie-tooth-disease#inheritance

http://www.charcot-marie-tooth.org/about_cmt/genetics.php

http://neuromuscular.wustl.edu/time/hmsn.html

The pattern of inheritance varies with the type of Charcot-Marie-Tooth disease.

Type 1, most cases of Type 2, and intermediate forms of Charcot-Marie-Tooth

disease are inherited in an autosomal dominant pattern. This pattern of

inheritance means that one copy of the altered gene in each cell is sufficient

to cause the disorder. In most cases, an affected person has one affected

parent.

Type 4 Charcot-Marie-Tooth disease and a few forms of Type 2 are inherited in an

autosomal recessive pattern, which means both copies of the gene in each cell

have mutations. Most often, the parents of an individual with an autosomal

recessive condition each carry one copy of the mutated gene, but do not show

signs and symptoms of the condition.

Type X is inherited in an X-linked dominant pattern. A condition is considered

X-linked if the mutated gene that causes the disorder is located on the X

chromosome. The inheritance is dominant if one copy of the altered gene is

sufficient to cause the condition. In most cases, affected males, who have the

alteration on their only copy of the X chromosome, experience more severe

symptoms of the disorder than females, who have two X chromosomes. A striking

characteristic of X-linked inheritance is that fathers cannot pass X-linked

traits to their sons. All daughters of affected men will have one altered X

chromosome, but may only have mild symptoms of the disorder.

Some cases of Charcot-Marie-Tooth disease result from a new mutation and occur

in people with no history of the disorder in their family. famfamily.and occur

in people with no history of the disorder in their family.