Severe, Early-Onset CMT
What is severe, early-onset CMT?
Severe, early onset CMT is a subtype of CMT that is a particularly severe variant of the disease. Other terms used to describe this variant include CMT3, Dejerine-Sottas disease, and congenital hypomyelinating neuropathy.
The use of the terms “Dejerine-Sottas disease” and “congenital hypomyelinating neuropathy” began prior to the identification of the genetic defects currently used to classify CMT patients into subtypes. Therefore, many of the same genes that cause other subtypes of CMT also cause these disorders; however, patients are more severely affected.
In general, the Dejerine-Sottas Disease subtype is used to classify patients who have a particularly severe form of CMT with onset of the disease prior to three years of age. Congenital hypomyelinating neuropathy describes patients whose disease is recognized even earlier, usually during infancy.
What are the symptoms of severe, early-onset CMT?
Severe, early-onset CMT is a severe neuropathy (disease or abnormality of the nerves), with generalized weakness sometimes progressing to profound disability, loss of or changes in sensation, curvature of the spine and sometimes mild hearing loss. Severe, early-onset CMT begins in infancy or early childhood, and progresses slowly. Severe disability may eventually occur.
For more, see Signs and Symptoms.
What causes severe, early-onset CMT?
Severe, early-onset CMT is caused by defects in the genes for proteins found in axons, fibers that carry electrical signals between the brain and spinal cord and the rest of the body, or in the genes for proteins found in myelin, a coating on axons that insulates and nourishes them. Some of these same genes also cause CMT1 and CMT2 such as PMP22, MPZ, and GJB.
Severe, early-onset CMT can be inherited in either an autosomal dominant or recessive pattern. For more, see Causes/Inheritance.