A 33-year-old-woman who was diagnosed with chronic fatigue syndrome several years ago noticed a ‘heavy feeling’ and progressive weakness of the upper legs over a period of four months. Climbing stairs became very difficult, and eventually she could no longer walk independently. She did not complain about weakness in her arms. There were no sensory complaints. During the past months, her voice had changed. Especially if she was tired, she would speak ‘like a drunk’. There were no complaints about double vision, drooping eyelids, or swallowing. There were no clear symptoms of autonomic dysfunction. She did not drink alcohol but had smoked at least a pack of cigarettes per day for over 10 years.