CMT-SORD
CMT-SORD is one of the most recently identified forms of CMT, described in 2020. It is caused by losing an enzyme called sorbitol dehydrogenase, which lets a sugar alcohol build up to levels that are toxic to nerves. It is an unusually active area of drug research.
What CMT-SORD is
CMT-SORD is caused by changes in the SORD gene that switch off an enzyme called sorbitol dehydrogenase. Normally this enzyme breaks down sorbitol, a sugar alcohol the body makes. Without it, sorbitol builds up, and at high levels it becomes toxic to the long nerves that reach the feet and hands.
The result is an axonal neuropathy: the nerve fibers themselves are damaged, so nerve testing tends to show reduced signal strength rather than slowed speed. It typically causes a slowly progressive, mostly motor weakness, with about half of people also reporting sensory symptoms.
CMT-SORD was only identified as a distinct cause of CMT in 2020, and it turned out to be one of the more common recessive causes. Because the underlying problem is a measurable buildup of sorbitol, it has become an active target for drug research aimed at lowering those levels.
How common it is. Since its discovery in 2020, CMT-SORD has been found to be one of the more common recessive (both-parents) causes of axonal CMT.
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.
- Slowly progressive weakness and wasting of the feet and lower legs, often more motor than sensory
- Foot drop, high arches, and difficulty running, frequently noticed in the teenage years
- Reduced or absent ankle reflexes
- Sensory symptoms in about half of people
- A raised level of sorbitol in the blood, which can help support the diagnosis
Onset and how it changes over time
CMT-SORD usually begins in the first or second decade of life, with reported onset often in the teenage years, and progresses slowly. As with other forms of CMT, severity varies from person to person.
CMT-SORD is generally slowly progressive and not life-limiting. Because the underlying sorbitol buildup can be measured and, in principle, targeted, this subtype is a particularly active focus of current research, which makes an accurate genetic diagnosis especially worthwhile.
How it is inherited
CMT-SORD is inherited in an autosomal recessive pattern, which means it takes two changed copies of the SORD gene, one from each parent, to cause it. Parents are usually unaffected carriers. When both parents carry a change, each child has about a 1 in 4 (25 percent) chance of being affected and a 1 in 2 chance of being a carrier. A genetic counselor can explain what this means for siblings and family planning.
Autosomal recessive inheritance
It takes two changed copies, one from each parent, to cause CMT. When both parents are unaffected carriers, each child has about a 1 in 4 chance of being affected and a 1 in 2 chance of being a carrier.
- 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 CMT-SORD, in their own words.
Daniel Blevins
A veteran and adaptive athlete in Arizona who spent thirteen years watching his body decline before anyone told him he had CMT.
Read their story ›
Christopher Gullmans
A father in Finland with CMT-SORD, diagnosed only after his wife, a physician, took one look at his legs. He advocates as a parent as much as a patient.
Read their story ›Frequently asked questions
What is CMT-SORD?
CMT-SORD is one of the most recently identified forms of CMT, described in 2020. It is caused by changes in the SORD gene that switch off an enzyme called sorbitol dehydrogenase, which normally breaks down sorbitol, a sugar alcohol the body makes. Without the enzyme, sorbitol builds up and at high levels becomes toxic to the long nerves that reach the feet and hands. If you want to confirm your subtype, genetic testing can identify it.
What causes CMT-SORD?
The result of losing the sorbitol dehydrogenase enzyme is an axonal neuropathy, meaning the nerve fibers themselves are damaged, so nerve testing tends to show reduced signal strength rather than slowed speed. It typically causes a slowly progressive, mostly motor weakness, with about half of people also reporting sensory symptoms. A raised level of sorbitol in the blood can help support the diagnosis.
How is CMT-SORD inherited?
CMT-SORD is inherited in an autosomal recessive pattern, which means it takes two changed copies of the SORD gene, one from each parent, to cause it. Parents are usually unaffected carriers. When both parents carry a change, each child has about a 1 in 4 (25 percent) chance of being affected and a 1 in 2 chance of being a carrier. A genetic counselor can explain what this means for siblings and family planning.
What are the symptoms of CMT-SORD?
CMT-SORD typically causes slowly progressive weakness and wasting of the feet and lower legs, often more motor than sensory. People frequently notice foot drop, high arches, and difficulty running in the teenage years, along with reduced or absent ankle reflexes. About half of people also report sensory symptoms.
Is CMT-SORD progressive, and is there research on it?
CMT-SORD usually begins in the first or second decade of life, progresses slowly, and is generally not life-limiting, though severity varies from person to person. Because the underlying sorbitol buildup can be measured and, in principle, targeted, this subtype is a particularly active focus of current research, which makes an accurate genetic diagnosis especially worthwhile. You can learn about participating through the GRIN registry.
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 peer-reviewed literature (Cortese et al. 2020 and later cohorts) and OMIM 618912. Verified 2026-07-08.