Eugenio Mercuri1, Francesco Muntoni2. 1. Pediatric Neurology Unit, Catholic University, Policlinico Gemelli, Rome 00168, Italy. Electronic address: mercuri@rm.unicatt.it. 2. Dubowitz Neuromuscular Centre and MRC Centre for Neuromuscular Diseases, UCL Institute of Child Health and Great Ormond Street Hospital for Children, London, UK.