CMT2A is caused by autosomal dominant mutations in the MFN2 gene. Autosomal recessive mutations in this same gene are associated with causing CMT2A2B. CMT2A has also been called CMT2A2A, CMT2A1, and CMT2A2.
The cause of CMT2A was originally thought to be autosomal dominant mutations in the KIF1B gene. When scientists identified that autosomal dominant mutations in the MFN2 gene were the actual cause, the CMT2A associated with the KIF1B mutations became 2A1, and the type associated with the autosomal dominant mutations in the MFN2 gene became CMT2A2. Scientists now believe that no mutations within the KIF1B gene are associated with causing any type of CMT. For this reason, amongst others, CMT2A1, CMT2A2, and CMT2A2 are simply now known as CMT2A.
CMT2A symptoms usually start to occur anywhere between early childhood and early adulthood, but most CMTers who have CMT2A experience symptom onset in early childhood. CMTers who have CMT2A will usually experience a particularly severe CMT. CMT2A is also sometimes referred to as Severe Early Onset Axonal Neuropathy.
It’s common for CMTers whose CMT2A is early onset to become wheelchair-dependent at a relatively young age, though this is not guaranteed because of the wide variability within even the same family. Some CMTers who have CMT2A might experience optic nerve atrophy, myelopathy, and cerebral dysfunction. CMTers who have CMT2A usually experience significant proximal weakness (the muscles closest to the center of the body), too.
The nerve conduction characteristic hallmarks of CMT2A are low or absent sensory and motor nerve amplitudes, and somewhat slowed conduction velocities that can range from ~37 meters/sec to the normal ~50 meters/sec.