The clinical story could be consistent with mitochondrial dysfunction. To be sure about the biopsy, it should be reviewed by a pathologist with experience in mitochondrial disorders. Also, muscle biopsies for mitochondrial disease typically have the typical biopsy evaluation, but then you can also have the actual mitochondrial enzymes (steps in the energy process) tested. YOu should ask your CCF neurologist if this additional testing was done, and if he/she thinks the special muscle or skin biopsy should be performed. Good luck.
My mother has very similar symptoms, including muscle pain, neurological symptoms, and fatigue, and was diagnosed with chronic fatigue syndrome. My father has many medical problems including digestive dysmotility, pancreatic insufficiency, heart arythmia, and history of blood clots.