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 27-year-old woman consulted the neurology clinic because of progressive muscle weakness in legs and arms. She noticed increasing difficulty in walking, with a maximum walking time of 15 minutes when there was a slight upwards slope, climbing stairs, and lifting heavy things. She had more and more frequent falls in which it felt like her legs suddenly could not bear her weight anymore. Once she fell, she wasn’t able to get up from the floor without help. At the time of referral, she also experienced problems rising from a sitting position. She also mentioned problems with repeated movements due to fatigability, for example, when she walked or was cleaning out the dishwasher.

In retrospect, she remembered that she had had a ‘typical’ walk from the age of five and had never been able to run. A subtle tremor of her fingers was already present in kindergarten. Her medical history was otherwise unremarkable. She had two healthy siblings.

A 41-year-old male was referred with a six-month history of progressive, exercise-related muscle pains, cramps, and muscle weakness. He also was found to have hyperCKaemia. His past medical history was unremarkable, and the family history was negative for neuromuscular disorders.

A 21-year-old man had for some years complained of diffuse pain and weakness of the legs. His sister was reported to have a severe disorder of the nerves or muscles. Their parents were reportedly not related.

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.

A 24-year-old man is the youngest of five children and of Turkish origin, who since the age of five years had noticed that he was not able to fully extend his arms. Furthermore, his Achilles tendons were taut. His previous history was unremarkable. An older brother had similar symptoms. Both had no cardiac symptoms. His parents were not affected.

A 23-year-old man gradually noticed slowly progressive difficulty running and climbing stairs and therefore he was referred. In retrospect, he had a hollow back since age 10, and when running, he had had difficulty keeping up with his peers. He had a younger brother with similar complaints. Serum CK activity was elevated (15 × ULN). EMG, which had been carried out by the referring neurologist, showed small motor unit action potentials.

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 55-year-old woman was referred because of increasing complaints about her legs for a few years. She had a continuous ‘heavy feeling’ in her legs and buttocks. There was no difficulty with walking or climbing stairs, but cycling was increasingly difficult. She had a dry mouth, which impaired swallowing.

A 73-year-old man was referred by his oncologist because of dyspnoea occurring for one and a half weeks, and high CK levels (1341 U/L). For four years he was treated for a melanoma with pulmonary and cerebral metastases. Treatment included nivolumab that had been started three months previously. The dyspnoea was worse on exertion and when lying down. He also experienced some difficulties speaking clearly, and choking had occurred a few times during the past week. He had no diplopia. The complaints did not fluctuate. There was some recent myalgia, but he had not noticed any muscle weakness.

A 52-year-old woman visited the neurologist because of drooping eyelids, which had not changed much over the past 10 years. She felt socially disabled because of the constant need to tilt her head upwards. Old photographs showed slight drooping from her mid-teens onwards. At one point she had experienced transient double vision. Speaking, swallowing, and limb muscle strength were reportedly normal. The family history was negative.

A 68-year-old woman was referred because of slowly progressive difficulty climbing stairs. Four years earlier, she had had ptosis surgery of both eyes. Her mother had been diagnosed with progressive external ophthalmoplegia at the age of 69 years. She denied having swallowing difficulties, but her daughter stressed that eating biscuits took her much longer than others.

A boy was born at 33 weeks’ gestational age via caesarean delivery because of a transverse position and difficulties in obtaining an adequate cardiotocography. Pregnancy had been complicated by fetal growth restriction with an abdominal circumference at p10, and polyhydramnios. His mother had noticed a reduction in fetal movements the day before delivery. Immediately after birth, he was hypotonic, pale, bradycardic, and without spontaneous breathing. Resuscitation was started with bag and mask ventilation and thoracic compressions. Heart rate and oxygen levels quickly normalized. However, breathing remained insufficient. Arterial CO2 levels rose to 14.0 kPa (ref 4.7–6.4) and he was intubated. He was the first child of unrelated parents. His mother had been diagnosed with obesity and gestational diabetes. The maternal grandmother had a sister whose daughter had a son who had died two days after birth more than 20 years earlier.

A 12-year-old boy had a three-year history of exercise-induced pain in his limbs; in particular, the shoulders, elbows, and knees were affected. For six months he had also experienced loss of strength. He noted difficulty with walking and cycling and was hardly able to climb stairs. He developed toe walking and complained about an itchy skin rash with focal depigmentation at his neck and trunk, diagnosed as eczema. He did not complain about swallowing difficulty, yet he became cachexic because his nutritional intake was lagging, and he suffered from mood swings.

Previous history was unremarkable. His parents were healthy, as was his older brother.

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.

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.

A 49-year-old man, who had always been very active, noted backache and pain in his neck starting four years ago. During this period, it became more difficult to rise from a chair and from his bed, to climb the stairs, or to carry heavy objects. Walking became a bit more difficult over time. He still went to the gym, but noticed that flexing his knees against resistance became more difficult. He slept well, could easily lie flat during the night, and did not experience myalgia, and there were no sensory disturbances. There were no symptoms of respiratory insufficiency. Family history was unremarkable.

A 33-year-old man was referred because of winging of the right scapula. History taking disclosed that seven months prior to referral he had experienced excruciating pain in the neck, irradiating to the right arm and thumb. The pain, which was particularly severe in the right scapular region, kept him initially awake and lasted for approximately six weeks. A week after the pain had started, he noticed having difficulty raising his right arm and hand. The latter is no longer present but at referral he still had a right-sided winged scapula and sensory disturbances of the radial part of the right medial forearm and of part of his thumb. Family history was negative for neuromuscular diseases.

A 38-year-old woman was referred to a dermatologist because of a rash in the face. She had been feeling low in energy for several months and in the past two months her arms and legs felt weak accompanied by myalgia. The rash had expanded to the extensor surfaces of hands and knees, upper chest, and neck. Serum CK was 4313 U/L (20 × ULN), and she was referred to the outpatient department for neuromuscular disorders with a presumed diagnosis of dermatomyositis.