Most demyelinating forms of Charcot-Marie-Tooth type 1 (CMT1) neuropathy are slowly progressive and do not respond to anti-inflammatory treatment. In nerve biopsy samples, overt lymphocytic infiltration is absent, but pathological features typical of macrophage-related demyelination have been reported. In mouse models of CMT1, demyelination was substantially reduced when the mutants were backcrossed into an immunodeficient genetic background. A few individual patients with CMT1 respond to anti-inflammatory treatment; however, unlike most patients with CMT1, these patients show accelerated worsening of symptoms, inflammatory infiltrates in nerve biopsies, and clinical features resembling chronic inflammatory demyelinating polyneuropathy as well as CMT1. We conclude that in patients with typical CMT1 and in animal models, a cryptic and mild inflammatory process not responsive to standard anti-inflammatory treatment fosters genetically mediated demyelination.