A five-month-old girl was referred with hypotonia and muscle weakness from birth onwards. She was born after an unremarkable pregnancy during a planned home birth at 40 weeks’ gestational age as the second child from healthy, unrelated parents. In the first days after her birth, they noted a paucity in movements and a low muscle tone. Breastfeeding failed, as she was unable to suck sufficiently. Bottle feeding with an adapted nipple also was a problem, and she often coughed or threw up after drinking. At the age of three months, a percutaneous endoscopic gastrostomy (PEG) probe had been placed to ensure caloric intake. Swallowing had gradually improved in the past month and now she managed to swallow small quantities of purified fruit and vegetables.

A 45-year-old man was referred by the internist because of a second episode of rhabdomyolysis. Motor milestones had been normal, and he had always been good at sports, although he was used to having stiff calves after skiing. At the age of 39 years he once experienced a sensation of ‘barbed wire’ in his upper legs, evolving in quite severe myalgia building up over days. This complaint dissolved in the course of three weeks. CK activity in this period increased to 23,094 U/L and normalized completely. There was no history of dark urine. In the absence of a metabolic cause or a history of the use of drugs, this was interpreted as having been caused by a viral infection. In the preceding months, he had been cycling fanatically daily, up to exhaustion. After this episode he had cut down on his sporting activities, but recently he had taken up mountain biking.