The Different Types

There are several different types of this disease, including: CMT1,CMT2, CMT3, CMT4, and CMTX. In CMT1 there are two main types (CMT1A and CMT1B). CMT1A is an autosomal dominant disease that results from a duplication of the gene on chromosome 17 which carries instructions for producing the peripheral myelin protein-22. Over expression of this gene causes the structure and function of the myelin sheath (an insulating layer that forms around nerves and is made up of protein and fatty substance) to be abnormal which causes the individual to experience weakness in the lower legs beginning in adolescence. CMT1B is also an autosomal dominant disease which is caused by a mutation in the gene that carries the instructions for manufacturing the myelin protein zero which is also a crucial component of myelin sheath. CMT1B produces symptoms similar to those found in CMT1A. CMT2 results from abnormalities in the axon of the nerve (the long threadlike part of a nerve cell along which impulses are conducted from the cell. The most common axonal form of CMT is caused by mutations in Mitofusin 2, a protein associated with mitochondrial fusion. CMT3-Dejerine-Sottas disease begins in infancy, it causes infants to have severe muscle weakness and sensory problems.This rare disorder can be caused by a specific point mutation in the P0 gene or the PMP-22 gene. CMT4 generally develop symptoms if leg weakness in childhood and by adolescence they may not be able to walk. CMTX is caused by a point mutation in the connexin-32 gene of the X chromosome.