What happens in Charcot-Marie-Tooth disease, exactly?

What is it?

Charcot-Marie-Tooth disease (CMT) is a genetic disease that causes progressive damage to the nerves that are supposed to transfer impulses between the central nervous system (the spinal cord and the brain) and the rest of the body. This leads to a loss of muscles as well as of sensation.

CMT is the most common inherited neurological disorder. It affects about 1 in 2500 people.

What causes it?

CMT is caused by a genetic mutation.  There are many different types of CMT and the way they are inherited is also different. Most, however, are inherited in a dominant manner. This means that in order to develop CMT you only need to get the faulty gene from one of your parents – it doesn’t help if you get a healthy gene from your other parent.

What happens during it?

Nerve cells have long “arms” called axons that transfer impulses forward. They are wrapped inside myelin sheets that protect them and help speed up the signals. The mutations behind CMT can affect either the axons or the myelin sheets.

In one form of CMT, the mutated gene codes for a protein that is very important for the myelin sheet cells. The mutation makes this vital protein abnormal, and this causes the myelin sheets to spontaneously break down. This is thought to first slow down the nervous signals, leading to the loss of sensation and muscle weakness, and sometimes to permanent damage to or even death of the neurons. Interestingly, this form of CMT doesn’t affect the sensation of temperature or pain, since these impulses are carried to the central nervous system in neurons that naturally don’t have myelin sheets.

You have probably heard that mitochondria are the powerhouses of the cell. They transfer energy into a form the cell can use. Nerve cells are whoppingly long (we’re talking in the cell scale of things here), and since energy is required also in the far end of axons, some mitochondria usually travel there. In another form of CMT, the mutation causes the mitochondria to clump together, making them unable to fit to the narrow axons. The far ends of axons are then left without energy and because of this they aren’t able to transmit impulses properly.

How can it be treated?

As with most genetic diseases, there is no established cure for CMT. It is an important goal to try to maintain muscle strength and movement for as long as possible, and moderate exercise as well as physiotherapy can be helpful in this.

 

 

Sources: https://en.wikipedia.org/wiki/Charcot–Marie–Tooth_disease, http://emedicine.medscape.com/article/1232386-overview?pa=LpO6RTJAbDreKJT9fHFV0JpUcmdUsmwJAPBoulPAoHFTC0eworT1y%2BcGZ%2Bd%2BbXvJVrJxKJt4DRD8mxYr6kYfOw%3D%3D#a5

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