CMT2M is caused by autosomal dominant mutations in the DNM2 gene. CMT2M is also known as Dominant Intermediate CMT Type B, or CMTDIB for short.
CMT2M symptom onset can occur anywhere between early childhood and the CMTer’s late 40s. Most CMTers who have CMT2M experience symptom onset in their late teens.
CMTers who have CMT2M will usually experience the classic CMT symptoms of lower limb weakness and atrophy resulting in gait abnormalities with frequent trips and falls as a result. Nerve conduction studies show motor median nerve conduction velocities ranging from 24 meters/sec to 54 meters/sec. Generally, 38 meters/sec and above is considered axonal CMT, and below 38 meters/sec is considered demyelinating CMT.