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.