What's Charcot-Marie-Tooth disease type 1A?
Charcot-Marie-Tooth disease type 1A (CMT1A) is the most common inherited demyelinating disease of the peripheral nerves. It is caused by having an extra copy (a duplication) of the PMP22 gene, which the body uses to build the protective myelin coating around peripheral nerves.
| Also indexed as | OMIM:118220, MONDO:0007309 |
|---|---|
| Features mapped | 16 |
| Treatments mapped | 3 |
| Published sources | 6 |
| Last reviewed | 2026-08-04 |
Signs and symptoms
Foot dorsiflexor weakness
Weakness lifting the front of the foot (foot drop) is one of the most common first symptoms, which is why catching the toes and tripping can be an early sign.
Pes cavus
A high-arched foot (pes cavus) is a common feature and can become rigid enough to need surgery.
Limb muscle weakness
Muscle weakness in CMT1A is symmetrical and affects the limbs farthest from the center of the body first, with the legs usually weaker and affected before the arms.
Hammertoe
Hammer toes, where the toes curl downward, often occur alongside the high-arched foot.
Insidious onset
CMT1A usually comes on gradually, most often in the first two decades of life, and is frequently first noticed as difficulty walking or running.
Juvenile onset
Symptoms most often begin in the first two decades of life, frequently first noticed as difficulty walking or running.
Slowly progressive
CMT1A usually progresses slowly over many years. In adults the change can be gradual enough that it resembles ordinary ageing.
Peripheral neuropathy
The condition is a peripheral neuropathy: it affects the nerves serving the limbs, leading to weakness and reduced sensation in the feet and hands.
Decreased motor nerve conduction velocity
On nerve testing, electrical signals travel more slowly than normal along the motor nerves. This slowing of conduction, measured during nerve testing, is a hallmark of the demyelinating form of CMT.
Distal sensory impairment
Many people also have reduced sensation in the feet and lower legs, because CMT1A affects the sensory nerves alongside the motor nerves.
Steppage gait
Weak ankle muscles cause a high-steppage gait, lifting the foot unusually high to avoid dragging the toes.
Hyporeflexia
Reflexes are reduced or absent, which a clinician can detect on examination.
Autosomal dominant inheritance
CMT1A is inherited in an autosomal dominant pattern, meaning a single copy of the duplication is enough to cause it. It can also arise as a new (de novo) change in someone with no family history.
Distal amyotrophy
Along with weakness, the distal muscles waste and lose bulk over time (amyotrophy), with the legs typically affected before and more than the arms.
Distal muscle weakness
The muscles farther from the center of the body, especially in the lower legs and feet, tend to weaken. The legs are usually affected earlier and more severely than the arms.
Kyphoscoliosis
Curvature of the spine (scoliosis or kyphosis) can occur in CMT1A, alongside other bone and muscle features such as a high-arched foot and hammer toes.
How it is diagnosed
Charcot-Marie-Tooth disease, demyelinating, type 1A
Diagnosed using: PMP22 duplication genetic testing.
“Diagnosis is confirmed by finding respectively a PMP22 duplication, deletion or point mutation.”
Charcot-Marie-Tooth disease, demyelinating, type 1A
Diagnosed using: Nerve conduction study (electrophysiology).
“Electrophysiological evaluation is needed to determine whether the polyneuropathy is demyelinating.”
Charcot-Marie-Tooth disease, demyelinating, type 1A
Diagnosed using: Nerve sonography (ultrasound).
“Electrophysiological evaluation is needed to determine whether the polyneuropathy is demyelinating. Sonography of the nerves can be useful.”
Treatment and management
What the research describes, not a recommendation. Treatment decisions belong with your clinician.
This covers treatments that appear in the published research mapped here. Investigational and experimental therapies are not included, so their absence is a boundary of this map, not a sign they do not exist.
Orthotic devices for foot and ankle
Orthotic devices, such as braces fitted to the foot and ankle, are used to manage the foot and ankle deformities of CMT. They support walking but do not change the underlying nerve condition.
Used to help with: Charcot-Marie-Tooth disease, demyelinating, type 1A.
“Orthotic devices may be prescribed for the management of foot and ankle deformities caused by Charcot-Marie-Tooth disease (CMT).”
Physical, occupational and rehabilitation therapy
There is no drug that changes the course of CMT1A, so care is supportive and aimed at symptoms. It can involve a rehabilitation physician, a physiotherapist and an occupational therapist working together.
Used to help with: Charcot-Marie-Tooth disease, demyelinating, type 1A.
“Treatment is currently symptomatic and may include management by a rehabilitation physician, physiotherapist, occupational therapist and orthopaedic surgeon.”
Orthopaedic surgery
An orthopaedic surgeon may be part of the care team for CMT1A, for example to correct foot deformities that affect walking.
Used to help with: Charcot-Marie-Tooth disease, demyelinating, type 1A.
“…may include management by a rehabilitation physician, physiotherapist, occupational therapist and orthopaedic…”
What changes how it shows up
Carrying the genetic change is not the whole story. The factors below are described in the research mapped here as changing whether, or how strongly, the condition appears. They modulate how the genotype is expressed; they do not, on their own, cause or cure it.
PMP22 duplication (17p12)
CMT1A is caused by a duplication of the PMP22 gene on chromosome 17 (a 17p12 duplication), meaning the person carries an extra copy of this region.
Described as modulating: Charcot-Marie-Tooth disease, demyelinating, type 1A.
“…most commonly Charcot-Marie-Tooth type 1A (CMT1A; 17p12…”
How to read the evidence labels
Where this comes from
This guide is built from 6 published source(s). Every claim above links back to one of them. Click any source ID to read the original on PubMed.
Take it further
Printed, source-linked documents built from this condition's graph — ready to bring to an appointment or attach to a coverage request. Every claim carries its published source, the same as this guide.