Hi, I was wondering if anyone has any experience of this condition. Dss, age 13, has just been diagnosed with this following a muscle biopsy. This has hit a real nerve with me as my own son, from my first marriage, died from a very unpleasant muscular condition in 2009. Dss lives with his mum but spends 4/14 days with us so I'd really appreciate hearing from others who have experience of how this might progress, or how we might support his physical well being. At the moment he has no noticeable side effects other than discomfort in his legs after intensive exercise.