Department of Neurology, Maastricht University Medical Center, Maastricht, the Netherlands, and Department of Neurology, St Elizabeth Hospital, Curacao. Department of Neurology, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, the Netherlands. National Referral Center for Rare Neuromuscular Diseases, Hopital Pitie-Salpetriere and University Paris VI, France. Department of Medicine (Neurology), University Health Network, University of Toronto, Toronto, Canada. Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, the Netherlands. Department of Neurology, UKD and Center for Neurology and Neuropsychiatry, LVR Klinikum, Medical Faculty, Heinrich Heine University, Dusseldorf, Germany. Department of Neurology, Cedars-Sinai Medical Center, Los Angeles, CA, USA. Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya, Japan. CSL Behring, Pennsylvania, USA. Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. AZ St-Lucas, Gent, Belgium. Department of Neurology, Universitatsklinikum Wurzburg, Wurzburg, Germany. UZ Leuven, Leuven, Belgium. Department of Neurology, Helsinki University Central Hospital, Helsinki, Finland. Dolnoslaski Szpital Specjalistyczny, Poland. Samodzielny Publiczny Szpital Kliniczny, Lublin, Poland. Department of Neurology, Philipps University, Marburg, Germany.