What is CMT?
Charcot-Marie-Tooth disease (CMT) is one of the most common inherited disorders of the peripheral nerves, the nerves that carry signals between the brain and spinal cord and the muscles and senses of the arms, legs, hands, and feet. It is named for the three physicians who first described it, and it is also called hereditary motor and sensory neuropathy (HMSN). If you or your child has just been diagnosed, this page explains what CMT is, what to expect, and the steps that bring clarity.
What CMT does in the body
In CMT, the peripheral nerves do not work the way they should. In some types the protective insulation around the nerve (the myelin sheath) is affected, which slows the signals down. In other types the nerve fiber itself (the axon) is affected, which weakens the signals. Either way, the message between nerve and muscle gets weaker over time.
Because the longest nerves are usually affected first, symptoms typically begin in the feet and lower legs and later reach the hands. Muscles can slowly lose strength and bulk, often unevenly, which is what produces the foot and hand differences many people with CMT recognize. CMT can affect each person differently, even within the same family.
CMT is progressive, meaning it tends to change gradually over the years. For most people it is not life-threatening. A few rare types can affect breathing, swallowing, or other systems, which is one reason knowing your specific subtype matters.
Common signs and symptoms
Symptoms vary widely from person to person and by subtype. Many people first notice changes in the feet and ankles in childhood or early adulthood, though some types appear later. These are the signs clinicians see most often.
High arches (pes cavus) are one of the most common signs of CMT, though how often they appear depends on the subtype. Pes cavus is reported in about 36% of people with CMT2A and roughly 63 to 72% of people with CMT1A, and foot deformities overall affect up to 71% of people with CMT.
Source: Stino et al., foot measures in patients with pes cavus with and without Charcot-Marie-Tooth disease.
How CMT is diagnosed
Many people are first identified by a neurologist on clinical exam, often supported by nerve testing. The only way to confirm CMT and pin down the exact subtype, though, is a genetic test.
- 1 Clinical exam A neurologist looks for the pattern that defines CMT: weakness and sensory loss that begin in the feet and lower legs, foot deformities, reduced reflexes, and often a family history.
- 2 EMG / NCV testing Electromyography (EMG) and nerve conduction velocity (NCV) studies measure how well the nerves carry signals. They help classify CMT as demyelinating (slowed signals) or axonal (weakened signals).
- 3 Genetic testing Genetic testing is the only way to confirm CMT and identify the exact subtype. Knowing your gene matters, because emerging therapies target specific subtypes.
Wondering how to get tested? HNF’s CMT Genie guides you and your provider through patient-initiated genetic testing, so you can move from “a kind of CMT” to a confirmed subtype.
The main types of CMT
CMT is grouped by how the nerves are affected, which is what EMG and NCV testing help determine. Within each group, the specific gene defines your subtype. There are more than 100 genes known to cause CMT.
Want the gene-by-gene detail? See CMT Types & Subtypes.
CMT by the numbers
Figures from HNF’s GRIN registry, as of July 2026.
A note for newly diagnosed families
A CMT diagnosis can feel overwhelming, and the experience looks different for everyone. There is no single path, but there are practical first steps: confirm your subtype with genetic testing, connect with a clinician who knows CMT, and learn which medications and supplements can worsen neuropathy so you can discuss them with your doctor. You are not alone in this.
Frequently asked questions
Is CMT fatal?
No. For almost everyone with CMT, it does not shorten life. It affects how your nerves talk to your muscles, not the organs you need to stay alive.
Is CMT the same as muscular dystrophy?
No, although they can look alike from the outside, because both cause muscle weakness and wasting. CMT is a problem in the nerves that feed the muscles. Muscular dystrophy is a problem in the muscles themselves.
Will I need mobility aids?
Some people do and some never do. Plenty of people with CMT wear ankle braces or use other supports and stay active for life. How far it goes varies a lot between subtypes and between people, so nobody can promise you one outcome. What can be said is that losing the ability to walk is not the usual path.
Can my children inherit CMT?
It depends on which gene is involved. Most CMT is autosomal dominant, which means each child of a parent with CMT has roughly a 50% chance of inheriting it. Some forms are recessive, where a child needs a copy of the changed gene from both parents. Others are X-linked, passed on the X chromosome, and often affect sons more severely. A genetic counselor can tell you the pattern behind your own diagnosis and what it means for your family.
Is CMT always genetic?
Yes, CMT always comes from a change in a gene. That is not the same thing as inheriting it. Sometimes the change happens for the first time in you, which doctors call a de novo or spontaneous mutation, and neither parent carries it. That is why people are diagnosed with CMT in families where nobody else has it.
Is there a cure for CMT?
Not yet. No drug has been approved that slows CMT down or reverses it. Treatment today is about keeping you moving and comfortable: bracing, therapy, and sometimes surgery. Gene therapies and drugs aimed at specific subtypes are in trials now, which is one more reason to know which subtype you have.
What causes CMT?
Changes in the genes that build and maintain your peripheral nerves. Some of those changes affect the myelin sheath, the insulation wrapped around the nerve, which slows the signal down. Others affect the axon, the nerve fiber itself, which weakens it. More than 100 genes have been linked to CMT. The most common cause is an extra copy of the PMP22 gene, which produces CMT1A.
How is CMT diagnosed?
Usually in three steps. A neurologist examines you and asks about your family. Nerve conduction studies and EMG measure how well your nerves are carrying signals. A genetic test then confirms the exact subtype.
Is CMT the same as ALS?
No, and this is one of the first fears people have when they notice foot drop or thinning calves. ALS is a different and far more aggressive condition. CMT does not behave the way ALS does, does not affect your thinking, and does not shorten life for the vast majority of people.
Does CMT affect the brain or thinking?
No. CMT affects the peripheral nerves, the ones outside your brain and spinal cord. Memory, thinking, and intelligence are not affected.
At what age do symptoms usually start?
Most often in childhood or the teenage years, though onset and severity vary a lot by subtype. Some people are not diagnosed until adulthood, usually because their symptoms are mild.
Does CMT get worse over time?
Usually yes, but slowly, over years and decades rather than months. The pace varies enormously from one person to the next. Many people go long stretches with no real change rather than declining steadily.
Can CMT skip a generation?
It can look that way. It depends on the inheritance pattern, and recessive and X-linked forms in particular can leave gaps in a family tree. That confusion is one of the better reasons to see a genetic counselor.
Is exercise safe for someone with CMT?
Generally yes, and it is usually encouraged. Moderate, low-impact activity helps keep strength and mobility. Very heavy or high-resistance exercise can make fatigue and muscle damage worse for some people, so it is worth working with a physical therapist who knows CMT rather than guessing.
Do people with CMT have a normal lifespan?
Yes. For the vast majority of people, CMT does not shorten life expectancy.
Can CMT be prevented?
No, because it is genetic. What you can do is understand it. Genetic counseling and testing help families see the real level of risk and the reproductive options open to them.
Take the next step
Confirming your subtype opens the door to the right care and, increasingly, to subtype-specific research and trials. Start with genetic testing, then connect with a clinic that knows CMT.
Your data can power the next treatment. Join GRIN, HNF’s patient registry →