We report a family of intravenous immunoglobulin (IVIg)-responsive X-linked Charcot-Marie-Tooth disease Type 1 (CMT1X) with a novel gap junction protein 1 mutation. Two of three siblings in the family complained of subacute motor and sensory impairment, and their symptoms improved after the administration of IVIg. Additional IVIg treatment also resulted in similar improvement. The other also showed a mild improvement on IVIg. It has been suggested that an immune-mediated process is involved in the progression of neuropathy in CMT1X. The finding in our report provides evidence of susceptibility to immune-mediated demyelinating neuropathy in some form of CMT1X. Superimposed demyelinating neuropathy as well as a gradual deterioration of neuropathy over decades can be a clinical manifestation of CMT1X.