What Is Charcot-Marie-Tooth Disease?

Charcot-Marie-Tooth disease is the most common inherited disorder of the peripheral nerves, affecting roughly 1 in 5,000 to 6,000 people worldwide. Despite its name, it has nothing to do with teeth. CMT is named after the three physicians who described it in 1886: Jean-Martin Charcot, Pierre Marie, and Howard Henry Tooth. The disease gradually damages the nerves that run from the spinal cord to the hands and feet, leading to progressive muscle weakness, sensory loss, and characteristic foot deformities. Because CMT encompasses dozens of genetic subtypes that vary widely in severity and mechanism, living with it can look very different from one person to the next.

How Common CMT Is and Who Gets It

A meta-analysis pooling studies from multiple countries estimated the overall prevalence of CMT at about 18 per 100,000 people, with rates appearing somewhat higher in adults than in children and in males compared to females.¹ A population-based study in the Auckland region of New Zealand found an age-adjusted prevalence of about 16 per 100,000, translating to roughly one in every 6,400 people. That study also found the highest rates in people aged 50 to 64, which likely reflects the slow-progressing nature of the disease rather than a late-onset spike.² Prevalence estimates also vary by region. Northern Europe appears to have higher rates (around 31 per 100,000 in the meta-analysis) than other parts of the world, though whether that reflects true genetic differences or better diagnostic infrastructure is still debated.³

The Major Types and What Goes Wrong in Each

CMT is not one disease but a family of related conditions that share the outcome of progressive peripheral nerve damage. The classification system can feel overwhelming, but the broad strokes are useful to understand because the type you have shapes your symptoms, how fast things progress, and what treatments may eventually be available.

CMT1 and the Myelin Problem

CMT1 is the most common group, accounting for roughly 40 to 50 percent of all cases. These are “demyelinating” forms, meaning the protective myelin sheath around nerves becomes defective. The single most frequent subtype, CMT1A, is caused by a duplication of the PMP22 gene. Schwann cells, which wrap nerve fibers in myelin, end up overproducing a protein called peripheral myelin protein 22, and the excess disrupts the myelin sheath’s structure. Over time, the damaged myelin causes nerve signals to slow down, and the underlying nerve fibers themselves gradually deteriorate as well.⁴ CMT1A alone makes up about 41 percent of CMT cases in population-based studies.⁵

CMT2 and Axonal Transport

CMT2 forms are “axonal,” meaning the nerve fibers themselves are the primary target rather than the myelin. One of the better-understood subtypes, CMT2A, involves mutations in the MFN2 gene, which encodes a protein involved in mitochondrial fusion. When MFN2 is mutated, mitochondria in nerve cells cluster abnormally and fail to travel properly along the length of the axon.⁶ The longest peripheral nerves, those reaching the feet, depend heavily on mitochondria being in the right place at the right time to supply energy. When mitochondria can’t get there, the nerve fiber starves and degenerates. This explains why symptoms tend to appear first in the feet and lower legs and later spread to the hands.⁷

CMTX and the X-Linked Form

CMTX1 is the second most common form of inherited motor and sensory neuropathy overall. It results from mutations in the GJB1 gene, which codes for a gap junction protein called connexin 32. This protein forms channels that allow molecules to pass between different layers of myelin, something like shortcuts through the wrapping. When connexin 32 doesn’t work, nerve function suffers.⁸ Because the gene sits on the X chromosome, men (who have only one X) tend to be more severely affected than women. Over 450 different GJB1 mutations have been identified.⁹ CMTX can be diagnostically tricky because nerve conduction velocities in affected males often fall in an intermediate range, neither as slow as classic CMT1 nor as normal-looking as CMT2.¹⁰

CMT4 and Autosomal Recessive Forms

CMT4 subtypes are recessively inherited, meaning a person needs two faulty copies of the gene to develop symptoms. These tend to be more severe and often start earlier in life. Different CMT4 subtypes implicate different genes, but several converge on problems with how cells move materials around internally. CMT4C, for example, involves the SH3TC2 protein and disrupted endocytic pathways, while CMT4B1 involves the MTMR2 protein and membrane trafficking.¹¹ CMT4C is also characterized by early-onset scoliosis, which can be a clinical clue pointing toward this particular subtype.¹²

What CMT Looks and Feels Like

The hallmark symptom most people notice first is difficulty with their feet. Muscles that lift the foot and toes weaken, while the muscles that curl the foot downward stay relatively strong. That imbalance pulls the arch higher and the toes into a claw position, producing the characteristic “cavovarus” foot: a high arch with the heel turned inward.¹³ Foot drop, where the foot slaps down with each step because the ankle can’t lift properly, leads to a distinctive high-stepping gait. The deformity tends to worsen over time because the underlying nerve damage keeps progressing.¹⁴ Studies confirm that as CMT progresses from mild to moderate severity, the high arch and related foot deformities get measurably worse.¹⁵

Hand weakness and wasting of the small muscles in the hands often develops later, making fine motor tasks like buttoning clothes or opening jars more difficult. Sensory loss in the feet and lower legs is common, which can mean unnoticed blisters or sores. In severe cases, weakness can spread to the forearms and lower thighs, though most people with CMT1A retain the ability to walk throughout their lives.

Pain Is More Common Than People Think

CMT has historically been described as a “painless” neuropathy, but that reputation turns out to be wrong. One study of CMT1A patients found that 88 percent reported pain, with the feet being the most common location.¹⁶ Much of this pain is musculoskeletal, coming from the abnormal stresses that foot deformities and altered gait put on joints and soft tissue. About 18 to 30 percent of CMT1A patients experience neuropathic pain specifically, the burning, tingling, or allodynia-type pain that comes from nerve damage itself.¹⁷ The average intensity of neuropathic pain in one study was rated about 5.7 out of 10, which is not trivial.¹⁸ Numbness and tingling were the most frequent neuropathic symptoms, followed by burning sensations. If your clinician dismisses pain as “not a CMT thing,” the evidence says otherwise.

How CMT Is Diagnosed

Diagnosis usually starts with clinical suspicion: a family history of neuropathy, high-arched feet, distal weakness, and diminished reflexes in a young person are strong clues. Nerve conduction studies are the next step. In CMT1, nerve signals travel much slower than normal because of the damaged myelin. In CMT2, signal speed may be relatively preserved, but the strength of the nerve signals (the amplitude) is reduced because fewer nerve fibers are conducting.¹⁹ The distinction between demyelinating and axonal patterns on nerve conduction studies was once considered clean, but it turns out there are intermediate cases, especially in CMTX, where conduction can look nonuniform and asymmetric, sometimes leading to confusion with acquired inflammatory neuropathies like CIDP.²⁰

Genetic testing confirms the diagnosis. Because PMP22 duplication (the cause of CMT1A) accounts for such a large share of cases, it’s usually tested first. For patients who come back negative, next-generation sequencing panels covering dozens of CMT-related genes have become cost-effective tools, identifying a genetic cause in about a third of cases that were previously unsolved.²¹ These panels also reveal how many rarer subtypes have been hiding in the diagnostic shadows.²²

Telling CMT Apart from Acquired Neuropathies

One clinically important challenge is distinguishing demyelinating CMT from chronic inflammatory demyelinating polyneuropathy (CIDP), an autoimmune condition that can look similar on nerve conduction studies but is treatable with immunotherapy. Nerve ultrasound has emerged as a helpful differentiator. Peripheral nerves in demyelinating CMT are markedly and uniformly enlarged throughout, while CIDP tends to produce more focal or irregular nerve thickening. Studies using nerve ultrasound measurements at standardized sites in the arms and legs have achieved high sensitivity and specificity for telling the two apart.²³ Adding lower-extremity ultrasound measurements to the standard upper-extremity screening appears to improve accuracy even further.²⁴ Getting this distinction right matters enormously, because someone with CMT won’t respond to immune-suppressing drugs, and missing CIDP means missing a chance for real improvement.

Managing Symptoms Today

There is no cure for CMT yet, so current management focuses on maintaining function and preventing complications. Ankle-foot orthoses are the most widely used assistive devices. They support the foot during walking, compensating for foot drop and reducing the energy cost of getting around. A systematic review found that ankle-foot orthoses do appear to improve several gait and balance measures, though the evidence base is limited by small study sizes and wide variability in device designs.²⁵ The review stressed the importance of customizing the brace to each individual, since the pattern and severity of weakness varies so much between patients.

When foot deformity becomes rigid, painful, or unmanageable with bracing, surgery enters the picture. A common procedure combines soft-tissue releases (like cutting the tight plantar fascia), tendon transfers to rebalance the pull of muscles across the foot, and bone-cutting procedures to flatten the arch. One series of 24 surgical corrections of cavus feet in CMT patients reported good to excellent results in over 90 percent of cases at an average six-year follow-up, with significant improvements in foot alignment.²⁶ Another study focusing on flexible deformities found that 77 percent of patients had less pain after surgery, 70 percent could walk barefoot, and 90 percent were satisfied with the correction of their deformity.²⁷ A critical detail: surgery works best when the deformity is still flexible. Once the bones become rigidly fixed, more extensive and less predictable procedures are needed. Timing the discussion with an orthopedic surgeon matters.

Emerging Therapies and Where the Science Stands

The most active area of therapeutic research targets CMT1A, because it has a single well-defined genetic cause and is the most common subtype. If the problem is too much PMP22 protein, the logical approach is to turn the gene down.

PXT3003, a combination of three repurposed drugs (baclofen, naltrexone, and sorbitol), was designed to reduce PMP22 overexpression through multiple pathways.²⁸ Early trials showed promising signals, but the drug’s journey has been rocky. A recent phase III trial in Chinese patients with CMT1A failed to meet its primary endpoints, a setback that has tempered enthusiasm even though two earlier trials had shown efficacy.²⁹

Antisense oligonucleotides, synthetic strands of genetic material that can silence specific genes, have shown striking results in mouse models. In two CMT1A rodent models, antisense treatment suppressed PMP22 and, when started even after disease was already established, restored myelination and nerve function nearly to normal levels.³⁰ The “even after disease onset” part is important, because it suggests treatment might help people who already have symptoms, not just prevent damage. These findings remain preclinical, but they represent one of the more credible paths toward disease-modifying treatment.

For axonal CMT forms, where the nerve fibers themselves degenerate, researchers have looked at blocking SARM1, a protein that drives axon destruction. Unfortunately, blocking SARM1 with a viral delivery approach did not improve the neuropathy in three different CMT mouse models.³¹ A more promising angle involves HDAC6 inhibitors, which appear to fix the mitochondrial transport problem that drives CMT2A. In cell-based models of both CMT2A and CMT2D, HDAC6 inhibitors improved mitochondrial movement along axons and rescued nerve function.³²³³ In a zebrafish model of CMT2A, an HDAC6 inhibitor also rescued motor deficits. These are early-stage findings, but HDAC6 inhibition may eventually address a range of axonal CMT subtypes that share transport problems as a root cause.

Tracking Disease With Blood Tests

One of the biggest obstacles to running clinical trials for CMT is that the disease progresses so slowly that measuring change over the course of a one- or two-year study is difficult. Physical examination scores shift only slightly between visits, making it hard to tell whether a drug is working. Neurofilament light chain, a protein released when nerve fibers are damaged, has emerged as a potential blood-based biomarker. Plasma levels of neurofilament light are significantly higher in people with CMT than in healthy controls and correlate with disease severity.³⁴ This has been confirmed across demyelinating and axonal CMT subtypes.³⁵ Longitudinal studies have shown increases in certain subtypes like CMT1B, CMT1X, and CMT2A compared to controls, though the pattern isn’t uniform across every subtype.³⁶ If neurofilament light chain proves reliable as a trial readout, it could dramatically speed up the development of new therapies by giving researchers a faster signal of whether nerve damage is slowing down.

Living With CMT and Quality of Life

Beyond the physical symptoms, CMT takes a broader toll that often goes underappreciated. Systematic reviews have found that people with CMT face reduced quality of life and significant sleep disruption.³⁷ Fatigue is one of the most common complaints, and restless legs syndrome appears at elevated rates. Survey data confirm that these sleep-related problems independently contribute to poorer health-related quality of life, separate from the direct effects of muscle weakness.³⁸ If you have CMT and are struggling with exhaustion that seems out of proportion to your weakness, bring it up. It’s a recognized part of the disease, not something you’re imagining.

Pregnancy and Family Planning

Because CMT is genetic, family planning is a frequent concern. The inheritance pattern depends on the subtype. CMT1A follows autosomal dominant inheritance, meaning each child of an affected parent has a 50 percent chance of inheriting the gene duplication. CMTX1 is X-linked, so daughters of an affected father will all carry the mutation (but may have milder symptoms), while sons will not inherit it from their father. CMT4 forms are recessive, requiring both parents to be carriers.

Preimplantation genetic testing is available and has been used successfully. In one series, embryos were tested before transfer, and five healthy babies were delivered across six treatment cycles, with a delivery rate of 50 percent per transfer cycle.³⁹ A more recent study using a direct detection method for the PMP22 duplication also reported successful outcomes and no increased complications from anesthesia in women with CMT1A undergoing the procedure.⁴⁰

For women already pregnant, the data from an Italian national registry are reassuring. Pregnancy outcomes and newborn health in women with CMT were broadly similar to the general population, although slightly higher rates of placenta previa, abnormal fetal presentations, and preterm delivery were observed.⁴¹ Having CMT does not preclude a healthy pregnancy, but it does warrant closer monitoring by a team aware of the diagnosis. Some women report worsening of symptoms during pregnancy, likely related to weight changes and fluid retention compressing already-vulnerable nerves, though symptoms often improve after delivery.

Preclinical Models and What They Tell Us

Much of what we know about CMT mechanisms comes from transgenic animal models, primarily mice but also fruit flies and zebrafish. These animals are engineered to carry the same gene mutations found in human patients, and when they develop a similar phenotype, such as gait abnormalities, reduced nerve conduction velocity, or thin myelin, they become platforms for testing drugs.⁴² One recent example is a nano-formulated curcumin compound that improved sensorimotor function and peripheral myelination in two different CMT1A rat models, while also appearing to dampen inflammatory pathways in the diseased nerve. The treatment showed a high safety margin in both in-vivo and in-vitro testing.⁴³ Whether these preclinical successes will translate to human benefit remains the perennial question, but the pipeline is more active now than at any point in CMT’s history.