CMT2A
CMT2A is the most common axonal (type 2) form of CMT. It is caused by changes in the MFN2 gene, which keeps the energy factories inside nerve cells healthy. It often begins early and can be more severe than the common demyelinating forms.
What CMT2A is
CMT2A is caused by changes in the MFN2 gene, which makes a protein called mitofusin 2. Mitofusin 2 helps mitochondria, the tiny structures that power every cell, join together, move along the nerve, and stay healthy. Nerve cells have very long fibers and huge energy demands, so they are especially sensitive when mitochondria struggle.
Unlike CMT1A, where the insulation is the problem, CMT2A affects the nerve fiber (the axon) itself. This is why it is called an axonal neuropathy, and why nerve conduction studies often show relatively normal speeds but weaker signals.
CMT2A is often one of the more severe forms of CMT. Many people have onset in early childhood and more significant weakness, though the range is wide, and some have a milder, later-onset course. Some people also develop optic atrophy, a thinning of the nerve to the eye that can affect vision.
How common it is. CMT2A is the most common of the axonal (type 2) forms of CMT, accounting for about 3 to 7 percent of genetically confirmed cases in large patient cohorts.
Common signs and symptoms
Reported symptoms and their severity vary from person to person, even within the same family. This is a general picture, not a prediction for any one person.
- Weakness and wasting of the feet and lower legs, often beginning in early childhood
- Foot drop, high arches, and difficulty walking or running, sometimes progressing to the hands
- Reduced or absent reflexes and reduced sensation in the feet
- A tendency toward earlier onset and greater severity than the common demyelinating forms, though this varies widely
- In some people, optic atrophy (thinning of the optic nerve) that can affect vision
Onset and how it changes over time
CMT2A frequently begins in the first years of life, and children may be later to walk or may struggle with running and frequent falls. That said, the severity varies a great deal, even within a family, and some people are not diagnosed until adulthood and stay relatively mild.
When onset is early, CMT2A can progress to more significant disability than the common demyelinating forms, and some people use mobility aids over time. It is generally not life-limiting. Because the course is so variable, an experienced care team is the best guide to what to expect for any one person.
How it is inherited
CMT2A is usually inherited in an autosomal dominant pattern, so a single changed copy of MFN2 is enough to cause it, and an affected parent has about a 1 in 2 (50 percent) chance of passing it to each child. New (de novo) changes are common, so many children with CMT2A have no family history. A small number of families show a recessive pattern instead. A genetic counselor can help sort out which applies to you.
Autosomal dominant inheritance
One changed copy of the gene is enough to cause CMT. A parent who has it passes it to about half of their children, on average, sons and daughters alike.
- Affected
- Carrier
- Unaffected
- Male
- Female
This diagram shows a typical family. Real families vary, and it does not predict any specific outcome. A genetic counselor can walk through what it means for yours.
Faces of CMT
Real families living with CMT2A, in their own words.
Grace Caldarone · Grace's Courage Crusade
A mother and daughter living with CMT2A, turning their family's mission into research, books, and school outreach.
Read their story ›
Elliot · Iris Adler's H.E.L.P. Fund
A grandmother's fund for her grandson Elliot, who lives with CMT2A.
Read their story ›
Skyler Fisher
Diagnosed at 13, now an elite para triathlete training at the U.S. Olympic & Paralympic Training Center and studying to work with animals.
Read their story ›
Julie Stone
Foot drop at six, a diagnosis at 28, and a family history nobody had mentioned. Now a personal trainer whose clients also live with CMT.
Read their story ›Frequently asked questions
What is CMT2A?
CMT2A is the most common axonal (type 2) form of Charcot-Marie-Tooth disease. It is caused by changes in the MFN2 gene, which makes a protein called mitofusin 2 that helps mitochondria, the tiny structures that power every cell, stay healthy inside nerves. Unlike CMT1A, where the insulation around nerves is the problem, CMT2A affects the nerve fiber (the axon) itself. If you want to confirm which subtype you have, genetic testing is the way to know for certain.
What gene causes CMT2A?
CMT2A is caused by changes in the MFN2 gene, which makes mitofusin 2. This protein helps mitochondria join together, move along the nerve, and stay healthy. Because nerve cells have very long fibers and huge energy demands, they are especially sensitive when mitochondria struggle.
How is CMT2A inherited, and will my children get it?
CMT2A is usually inherited in an autosomal dominant pattern, so a single changed copy of MFN2 is enough to cause it, and an affected parent has about a 1 in 2 (50 percent) chance of passing it to each child. New (de novo) changes are common, so many children with CMT2A have no family history, and a small number of families show a recessive pattern instead. A genetic counselor can help sort out which applies to you.
What are the symptoms of CMT2A?
CMT2A often begins with weakness and wasting of the feet and lower legs in early childhood, along with foot drop, high arches, and difficulty walking or running that sometimes progresses to the hands. Reflexes are often reduced or absent and sensation in the feet can be reduced. Some people also develop optic atrophy, a thinning of the nerve to the eye that can affect vision.
Is CMT2A progressive or severe?
CMT2A is often one of the more severe forms of CMT, and when onset is early it can progress to more significant disability than the common demyelinating forms, with some people using mobility aids over time. That said, the severity varies a great deal, even within a family, and some people are not diagnosed until adulthood and stay relatively mild. It is generally not life-limiting, and because the course is so variable, an experienced care team is the best guide to what to expect.
Confirm your subtype
If you have a clinical CMT diagnosis but no confirmed gene, genetic testing is how you learn your subtype. CMT Genie helps you and your provider get tested and connects you with telehealth genetic counseling.
Clinical information on this page is based on GeneReviews (Charcot-Marie-Tooth overview, NBK1358) and OMIM 609260. Verified 2026-07-08.