A 49-year-old man noticed a diminished sensation in his feet. Two months later, climbing stairs became difficult due to proximal muscle weakness of his legs. Over the next three months, sensory disturbances and both proximal and distal weakness progressed in arms and legs requiring the use of a walker or a wheelchair. Besides COPD, he was previously in a healthy condition. Based upon ancillary investigations, he was initially diagnosed with chronic inflammatory demyelinating polyneuropathy (CIDP), had received a course of intravenous Ig (IVIg), and was subsequently treated with high-dose corticosteroids (60 mg/day). He did not smoke or use drugs such as nitric oxide.