A 20-year-old previously healthy man suddenly noticed that he was unable to run. The next day he could not climb the stairs and lost strength in his arms. He was admitted to hospital, and over the next hours he progressively lost muscle power in his arms and legs. Swallowing was progressively impaired, and he noticed minor tingling in both hands and feet. He had had a minor upper respiratory tract infection a week prior to admission.

A previously healthy, very active 68-year-old man, who usually cycled over 100 km several times a week, noticed progressive tingling in his feet and lower legs that increased over several weeks. This was followed by progressive weakness in the arms and legs exceeding a period of eight weeks. After three months of progression, weakness became so severe that he could not even walk without help. He did not use drugs or drink alcohol.

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.