Charcot-Marie-Tooth Disease (CMT)

What is Charcot-Marie-Tooth disease?

Charcot-Marie-Tooth disease (CMT) is a condition that affects the nerves that control muscle movements. There are six main types of CMT, all of which happen because of a genetic mutation you inherited from one or both parents.

CMT is the most common form of inherited peripheral neuropathy (neuropathy means “nerve disease”). Your peripheral nervous system includes any nerves that aren’t part of your spinal cord or brain. Its name comes from Greek and means “around” or “outside the center.”

Who does it affect?

CMT is possible in people of all races and ethnicities. It happens equally to men and people assigned male at birth and women and people assigned female at birth.

How common is this condition?

CMT is an uncommon condition overall. Research estimates put the number of people affected worldwide between 700,000 and 2 million.

How does this condition affect my body?

Charcot-Marie-Tooth disease is a disease that affects your peripheral nerves, causing problems with how signals travel through those nerves. To understand why, it helps to know a little more about neurons, which are a key type of cell that make up your nerves.

More about neurons

Neurons send and relay signals through your nervous system, using both electrical and chemical signals. Each neuron consists of the following:

• Cell body: This is the main part of the neuron.
• Axon: This long, arm-like section extends out from the cell body. The axon has several finger-like extensions at its end. These extensions are synapses, which convert electrical signals within the neuron into chemical signals. The synapses connect to other neurons nearby, passing chemical signals to them.
• Dendrites: These are small branch-like extensions (their name comes from Latin and means “tree-like”) on the cell body. Dendrites are the receiving point for chemical signals from the synapses of other nearby neurons.
• Myelin: This thin, fatty layer surrounds the axon of many neurons and acts as a protective coating. Neurons with a myelin-coated axon send and relay signals at different speeds than neurons without this axon coating.

CMT affects your neurons in two ways, and some conditions cause one of these more than the other.

• Myelin loss: CMT can affect the myelin coating on your axons, causing them to lose myelin entirely or to have too little of it in the first place. Either way, this affects the speed of the signals traveling through your neurons, slowing them down.
• Axon problems: When Charcot-Marie-Tooth disease causes the axons on your neurons to shrink or deteriorate, this weakens the signals sent or relayed through that neuron.

In some cases, some subtypes of CMT slow your nerve signals slightly. The effect is enough to cause symptoms but not enough for healthcare providers to determine whether the problem is due to myelin loss or axon problems. Experts call these “intermediate” subtypes.

The neurons in your body aren’t all the same length or size. The neurons that reach down your spine to your legs and feet are the longest. These longer neurons (which bundle together and form nerve fibers) are most likely to show the early effects of CMT. A similar effect is possible in your arms and hands, but this usually doesn’t happen early on in this disease.

What are the symptoms of Charcot-Marie-Tooth disease (CMT)?

CMT symptoms usually start in your early teenage years, but can start earlier during childhood or later during middle age. Issues usually appear and develop slowly, getting progressively worse over time.

CMT has two main types of symptoms depending on which types of nerve signals the condition affects. The affected signals are either motor or sensory.

• Motor: These signals travel from your brain to your muscles. They tell your muscles to move. Disruption in how motor signals travel means you have trouble moving your muscles, particularly in your limbs.
• Sensory: These signals travel from different places in your body to your brain. They tell your brain what’s happening to that part of your body right now. Disruptions in sensory signals affect how you feel sensations in your lower legs, feet and hands.

Motor symptoms

The motor symptoms of CMT affect your muscles. These include:

• Muscle weakness.
• Paralysis.
• Loss of muscle mass (muscle atrophy).
• Decreased or no reflexes.
• Hammertoes.
• Foot drop (a very high foot arch).
• Trips and falls because of gait disorders and changes in how the muscles in your legs and feet work.
• Repeated ankle sprains.
• Breathing problems (this usually only happens in severe cases).

Sensory symptoms

The sensory symptoms of Charcot-Marie-Tooth disease include:

• Numbness or tingling.
• Inability to feel heat or pain sensations in your lower legs, feet and hands.
• Creeping sensations in your legs.
• Chronic pain.
• Loss or decrease in other senses, especially vision and hearing (these are less common and usually only happen with specific subtypes of CMT).

What causes Charcot-Marie-Tooth disease?

Every one of your nerve cells holds some DNA, which they use like an instruction manual, telling them how to do their jobs. A DNA mutation is like a typo in your DNA. Your cells follow the instructions in your DNA very strictly, so mutations cause your cells to work incorrectly, which is how CMT happens.

CMT can involve mutations in one gene or several. So far, researchers have identified several dozen different gene mutations that can cause the different forms of CMT.

You can have a DNA mutation in one of two ways:

• Inherited: These DNA mutations pass to you from one or both parents.
• Spontaneous: You develop these mutations while you’re still an embryo developing in the uterus. They’re sometimes called “de novo” mutations, which means “new.”

Are there different types of CMT?

Yes, there are seven main types of Charcot-Marie-Tooth disease, but CMT types 1 and 2 are the most common. The other forms are very or extremely rare.

• CMT type 1 (CMT1): This type affects myelin, causing slowed signals. It usually appears between ages 10 and 40, but some people can live for decades without developing any symptoms. This is the most common type of CMT, happening about twice as often as CMT2.
• CMT2: This type involves axon problems. Nerve signals are weaker and may travel slightly slower, too. It accounts for about one-third of CMT cases.

Other types of CMT include:

• CMT3 (also known as Dejerine-Sottas disease).
• CMT X-linked (CMTX).
• Dominant intermediate CMT (CMTDI).
• Recessive intermediate CMT (CMTRI).

Is it contagious?

No, CMT isn’t contagious, and you can’t spread it from person to person.

How is Charcot-Marie-Tooth disease (CMT) diagnosed?

It usually takes a combination of methods for a healthcare provider to determine the exact type of CMT you have and determine your case’s severity. The methods include a physical and neurological exam, lab tests, imaging and other diagnostic tests. They’ll also ask questions about your family medical history and your history and life circumstances.

What tests will be done to diagnose this condition?

The following tests are most likely with CMT:

• Electromyogram (especially nerve conduction tests).
• Genetic testing.
• Spinal tap (lumbar puncture) to test cerebrospinal fluid.
• Magnetic resonance imaging (MRI).
• Ultrasound.
• Evoked potentials (especially for CMT subtypes that affect your hearing and vision).
• Nerve biopsy.

How is Charcot-Marie-Tooth disease (CMT) treated, and is there a cure?

There’s no way to cure CMT or treat the condition directly. However, it’s usually possible to treat the symptoms and effects of this condition.

What medications/treatments are used?

Common treatments for CMT include:

• Physical therapy and occupational therapy.
• Leg braces, walkers, wheelchairs and other kinds of mobility support devices.
• Special footwear for changes in foot shape.
• Surgery to correct changes in the shape of your hands, feet, hips or back.
• Medications for some symptoms, especially chronic pain.

Other treatments for CMT are possible, but these vary depending on the specific subtype of the condition. Your healthcare provider is the best person to tell you the treatments most likely to help you, as they can give you information specific to your case and needs.

Your healthcare provider is also the best person to you more about the potential side effects or complications that can happen with the various treatments, and the recovery time you’ll need (if any) before you start to feel better or return to your usual routine.

How do I take care of myself or manage my symptoms?

Charcot-Marie-Tooth disease isn’t a condition you can self-diagnose because it requires specific medical tests. Some of the symptoms of CMT can also happen with other conditions, some of which are very serious. Because of that, you should always talk to a healthcare provider to learn if you have this condition and what you should do to manage it.

How can I reduce my risk of developing CMT or prevent it altogether?

Charcot-Marie-Tooth disease is a condition that either you inherit or that happens unpredictably. Because of this, there’s no way to prevent it or reduce your risk of developing it.

While you can’t prevent CMT from happening, genetic testing and counseling can help you know the chances that you’ll pass it on to your children. Your healthcare provider or a genetic counselor can tell you more about what this means for you and your available options.

Pregnancy with CMT

Most people who have CMT can still have children. However, some complications are possible or even more likely to happen. Many people with CMT who can become pregnant need additional care during the pregnancy or delivery. There’s also an increased risk of bleeding after giving birth.

Your healthcare provider can tell you more about whether or not these concerns are relevant to you and what you can do. They can also refer you to specialists, especially maternal-fetal medicine physicians specializing in more complicated pregnancies.

What can I expect with CMT, and what is its outlook?

In general, CMT isn’t a dangerous condition, except with specific subtypes of this disease that are very severe. Most people with CMT will develop problems with moving or using certain senses, but these rarely affect how long you live. With the help of special devices and other kinds of care, especially foot and ankle devices or footwear, most people with Charcot-Marie-Tooth disease can still have a normal lifespan and live happy, fulfilling lives.

With the severe forms of this condition, the most dangerous issue is weakness in the muscles that control breathing and swallowing. These can lead to respiratory failure, pneumonia and other issues, which can become deadly. These are more likely when you develop CMT symptoms earlier in life, especially during childhood.

How long does CMT last?

CMT is a permanent, lifelong condition. You have it when you’re born, but most people don’t show its symptoms until they’re adults. There’s also no way to cure it, and it doesn’t go away on its own.

How do I take care of myself?

If you have CMT, your healthcare provider is the best source of information about what you can and should do to take care of yourself and manage this condition. They can also monitor the progress of your condition and recommend treatments or strategies to help you manage it.

In general, you should do the following:

• See your provider as recommended. This is especially important so your provider can monitor the progress of this condition and how it’s affecting you. They can also modify your treatment plan or offer suggestions about what you can do to help yourself.
• Follow your treatment plan. This means taking your medications as prescribed or using medical devices as your provider directs. These are very important because they can help you with the symptoms or slow down the rate at which some symptoms worsen.
• Avoid drugs or neurotoxic. These are drugs or substances that have a higher risk of damaging your nervous system. Your provider will likely encourage you to use alcohol with caution or not at all, as overuse can cause nervous system damage.

When should I see my healthcare provider, and when should I seek care?

Your healthcare provider will schedule regular follow-up visits to monitor your condition and symptoms. You should also call or see them if you notice any changes in your symptoms, especially ones that disrupt your usual activities or routine.

When should I go to ER?

Most people who have CMT won’t need emergency care unless they fall because of trouble controlling the muscles in their legs and feet. If you have a fall, you should seek care if there’s any risk of injury to your head, neck or back. That’s because damage to any part of your central nervous system could cause major complications with CMT.

Is Charcot-Marie-Tooth disease a form of multiple sclerosis?

Multiple sclerosis (MS) is a condition that causes inflammation of the myelin around neurons and nerve fibers in your brain and spinal cord. Certain types of CMT also involve those symptoms, but otherwise, they’re very different conditions.

Is Charcot-Marie-Tooth disease an autoimmune disease?

No, CMT isn’t an autoimmune disease. However, some mutations of the PMP22 gene, which are often the cause of CMT, can also increase your risk of developing some autoimmune conditions.

Does Charcot-Marie-Tooth disease affect the brain?

In general, CMT doesn’t directly affect your brain. For the most part, CMT affects longer neurons and nerve fibers, which make up your spinal cord and peripheral nerves, but not your brain. Some of the subtypes of CMT can cause minor changes in brain structure, but experts haven’t found evidence that this affects brain function in a noticeable or concerning way.

A note from Cleveland Clinic

Charcot-Marie-Tooth disease (CMT) includes several different conditions that affect your peripheral nervous system, the network of nerves that connect to your brain and spinal cord. This condition is most likely to affect your ability to control muscle movements and feel or sense the world around you. Many people with this condition need assistive devices or accessories, and some also need surgery or types of physical and occupational therapy. However, CMT usually isn’t a dangerous or life-threatening condition, and most people who have it have a normal lifespan and happy, fulfilling lives.