Mutations in the NEFL gene are linked to both CMT1F and CMT2E. Historically, doctors have referred to this as 1F/2E. This is because both subtypes are linked to this gene. But is there a difference?
CMT1F is a demyelinating subtype, and CMT2E is axonal. These two distinctions are based on nerve conduction study (NCS) results. If the results show a demyelinating CMT when you’re first diagnosed, it’s called CMT1F when a NEFL gene mutation is the cause. And when it’s an axonal CMT and an NEFL gene mutation, CMT2E.
Sometimes, NCS results show an intermediate neuropathy (nerve conduction is somewhere between axonal and demyelinating), and when this occurs with an NEFL gene mutation, it’s called dominant intermediate CMT G (CMTDIG). Regardless of NCS results, some doctors will classify it as CMT1F/2E.
Clinically, symptom-wise, there is no difference between CMT1F, CMT2E, and CMTDIG. There are no differences in symptoms, progression, severity, or age at onset. Most with CMT that’s caused by an NEFL gene mutation are diagnosed with CMT2E. Some are diagnosed with CMT1F. Others are told CMT1F/CMT2E. Still, others are told “NEFL” by their doctors. CMTDIG is rarely used. Whichever is the case, none are wrong, and each refers to the same thing. This is not uncommon in CMT. We see this with other genes and subtypes.
When looking for information on “NEFL-related CMT,” any info pertaining to CMT1F, CMT2E, CMT1F/CMT2E, or CMTDIG is relevant and applies. This holds true whether it’s symptom management, what to expect for progression/severity, or especially for research.
