CMT4J is caused by autosomal recessive mutations in the FIG4 gene. CMT4J is a very distinct type of CMT, and it is predominantly a motor neuropathy with no sensory involvement, or minimal sensory involvement.
CMT4J symptom onset can occur anytime between early childhood and the CMTer’s 50’s. Disease severity is as equally variable. Some CMTer’s who have CMT4J become wheelchair dependent by the time they are in their late teens, while others never do. Some CMTers who have CMT4J might experience severe scoliosis, while others will not experience scoliosis. Rarely do CMTers who have CMT4J experience sensory impairment. Sensory impairment is almost never associated with CMT4J.
CMTers who have CMT4J might experience motor milestone delays. Others might experience a condition called neurogenic bladder and/or neurogenic bowel. Some CMTers with CMT4J might experience a disease course that is severe enough to cause quadriplegia. Some CMTers who have CMT4J might experience an abrupt severe worsening/weakening of the limbs, while others might experience a mild and slowly progressive disease course.
Of interesting note, with CMT4J’s predominantly motor neuropathy, autosomal dominant mutations within the FIG4 gene (these mutations are different from the mutations that cause CMT4J) are associated with causing Amyotrophic Lateral Sclerosis Type 11, or ALS11 for short (OMIM 612577). By no means does this mean that CMT4J and ALS are connected. They are not. There is no published literature that suggests a connection of any kind, and not even remotely.