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12 | InTouch AUTUMN 2026 First described in 1886 by three physicians – Jean-Marie Charcot, Pierre Marie, and Howard Henry Tooth, Charcot Marie-Tooth (CMT) is a group of relatively common genetic neurological conditions, occurring in approximately 1 in 2,500 people worldwide. What is Charcot-Marie-Tooth Disease? YOUR CONDITION IN REVIEW CMT is also commonly known as Hereditary Motor and Sensory Neuropathy (HMSN) or Peroneal Muscular Atrophy and comprises a number of disorders that affect the peripheral nerves (e.g. those of the hands and the lower legs). A nerve cell transmits information throughout the body by sending electrical impulses along a long extension of the cell called the axon. To increase the speed and efficiency of these signals, the axon is wrapped in myelin, an insulating layer produced by specialized cells called Schwann cells. This myelin sheath allows electrical impulses to travel rapidly and reliably along the axon. When either the axon or its myelin covering is damaged, peripheral nerves cannot properly activate target tissues – including muscles, skin, and internal organs – or effectively carry sensory information from the body back to the brain. CMT is caused by mutations in genes that produce proteins involved in the structure and function of either the peripheral nerve axon or the myelin sheath. More than 100 genes have now been identified as causing different forms of CMT. The degeneration of the peripheral nerves may result in reduced sensation (i.e., the ability to feel heat, cold, and pain) as well as muscle weakness and atrophy. In most cases, the gene mutations in CMT are inherited. How is Charcot-Marie-Tooth Disease inherited? The human genome consists of 23 paired chromosomes, which contain genes composed of DNA. Twenty-two pairs of chromosomes are autosomes, meaning they are not involved in sex determination. The 23rd pair consists of the sex chromosomes, with males having one X and one Y chromosome, and females having two X chromosomes. There are three main ways in which CMT can be inherited. • Some forms are inherited in an autosomal dominant fashion, which means that only one copy of the altered gene is needed to cause the condition. Children of an affected parent have a 50% chance of inheriting it. • Other forms are autosomal recessive , which means that both copies of the altered gene must be present for the condition to develop. In this case, both parents are carriers of the altered gene, and each child has a 25% chance of being affected. • Still other forms are inherited in an X-linked manner, which means that the altered gene is located on the X chromosome. Females, who have two X chromosomes, may compensate if only one X chromosome carries the mutation, although some may still have symptoms. Males, who have one X and one Y chromosome, lack this compensatory ability and are therefore often more severely affected. An affected male cannot pass an X-linked condition to his