CMT4E is caused by autosomal recessive mutations in the EGR2 gene. Autosomal dominant mutations in this gene cause the demyelinating type CMT1D. CMT4E is also called Congenital Hypomyelinating Neuropathy Type 1, or CHN-1 for short.
CMT4E seems to affect only one family. Symptom onset is at birth, all CMTers in this family were “floppy” at birth—suffering severe hypotonia, and each experienced significant milestone delays.
Nerve conduction studies in each CMTer in this family show that nerve conduction velocity was only 3 meters/sec (normal is considered ~50 meters /sec), and Compound Motor Action Potentials (CMAP) were extremely low or absent.