Can Be Homozygous or Can Be Compound Heterozygous
CMT2B4 is caused by autosomal recessive mutations in the MFN2 gene. Other mutations in this gene are associated with causing other types of CMT. CMT2B4 is also known as Autosomal Recessive CMT2D, or AR-CMT2D for short.
CMT2B4 symptoms usually start to occur by age 3. CMTB4 is a particularly severe type of CMT. CMTers who have CMTB4 will usually experience profound weakness and atrophy in the lower legs, ankles/feet, forearms, and hands. There is usually profound sensory loss also. On nerve conduction study, sensory responses are absent, but conduction velocities are only minimally slowed.