A 55-year-old man had had muscle complaints for as long as he could remember. He could not stretch his arms or walk without shoes due to deformities of the feet. Proximal muscle weakness was mild and slowly progressive over years, and contractures had always been prominent. His stamina was low, but he still worked full-time as a manual worker. He was otherwise healthy.

Family history revealed that his father was similarly affected. In addition, a half-brother and half-sister not only had contractures but also had muscle weakness. The latter underwent surgery for torticollis in the neonatal period.

A 39-year-old man was referred because of three attacks of severe myalgia accompanied by ‘bloody urine’. There were no complaints about muscle weakness. There had been preceding exercise, but not excessively. Prior to one attack, he had suffered from a viral infection.

During childhood, at sports he had often noticed having muscle ache, once accompanied by ‘red urine’. There was no ‘second wind’ phenomenon. After three days, the muscle complaints usually disappeared. At age 20 years he had suffered a similar attack during a soccer game and again at age 37 after playing volleyball. On that occasion, CK was determined and found to be approximately 800,000 IU/L, which led to admission to hospital for hydration and monitoring of his kidney function. His CK normalized rapidly. At that time, a muscle biopsy was performed that showed no accumulation of fat or glycogen and no mitochondrial abnormalities.

After a normal pregnancy without hydramnios, delivery of a healthy-looking girl was uneventful. At four months of age, she had had a respiratory infection and was noted to have a weak cough. At eight months of age she was just able to keep her head in an upright position but was not able to sit unsupported. Her mother admitted that she had not been very active since birth, but there was no progressive muscle weakness and no swallowing difficulty. She was referred to a paediatric neurologist because of a suspected neuromuscular disorder. The parents were healthy and there was no consanguinity.

A 35-year-old man complained about muscle stiffness and weakness, especially when initiating a movement. He had experienced these symptoms for as long as he could remember. They were present in his eyes, jaws, tongue, and limb muscles. He had noticed that cold weather had a negative influence. He was not able to run and did not participate in team sport activities. In spite of these symptoms, he experienced no limitations in activities of daily living. He was referred because he had been informed elsewhere about possible treatment. The family history revealed similar symptoms in a sister and a brother, but not in the parents. His father’s grandparents were cousins.

A 41-year-old man was referred because of persistent backache. When questioned, he recalled that he had had firm calves since childhood. Once, after strenuous exercise, he had experienced black coffee-coloured urine. At the time, he did not consult his GP.

In his late twenties, a 30-year-old man reported difficulty with raising his arms and running, which had progressed over subsequent years. During his teens he had been a very good soccer player.