NEFL and Charcot-Marie-Tooth disease: Typically, mutations in the neurofilament light chain (NEFL) gene cause Charcot-Marie-Tooth disease (CMT) type 2E (CMT2E; characterized by axonal damage in the peripheral nerves, leading to muscle weakness and sensory loss), CMT1F (which involves demyelination and slowed nerve conduction), and dominant-intermediate CMT (DI-CMTG; a form with both axonal and demyelinating features).