CMT4B2 is caused by autosomal recessive mutations in the SBF2 gene. Some literature suggests that autosomal recessive mutations in the MTMR13 gene are the cause of CMT4B2, but the evidence in publicly available published literature more significantly supports the autosomal recessive mutations in the SBF2 gene as the cause.
CMT4B2 symptom onset usually occurs by the time the CMTer is 10 years old. CMTers who have CMT4B2 usually experience difficulty with walking as the first clinical signs of their CMT. CMTers who have CMT4B2 often require mobility assistance by the time they are in their teens, but sometimes not until their early 40’s.
Sensory responses are usually absent in nerve conduction study, and nerve conduction velocity is usually significantly slowed to less than 22 meters/sec (normal is considered ~50 meters/sec).
Early onset glaucoma and hearing loss has also been associated with CMT4B2.