School of Medicine and Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. Children's Hospital of Pittsburgh, UPMC, 4401 Penn Avenue, Pittsburgh, Pennsylvania, 15224, USA. Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA. Boston Children's Hospital, Boston, Massachusetts, USA. University of Utah, Salt Lake City, Utah, USA. Vanderbilt University Medical Center, Nashville, Tennessee, USA. USF Health, Morsani College of Medicine, Tampa, Florida, USA. Children's National Health System, Washington, District of Columbia, USA. Great Ormond Street, UCL Institute of Child Health, London, UK. National Hospital for Neurology and Neurosurgery, London, UK. Ultragenyx Pharmaceutical Inc., Novato, California, USA.