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 40-year-old woman was referred because she complained about cramping and swelling of the hands and leg muscles for more than four years. The referring neurologist also found hyperCKaemia (> 10 × ULN). The symptoms bothered her when using her computer or when she was performing squats. She had never produced dark urine and she had never noticed muscle weakness. Previous disease history was inconspicuous except for goiter. The family history was negative for neuromuscular disorders.