Acknowledgements
We appreciate the participation of all patients and their parents in this study. We thank Arron Scott and Bryan Hepworth (Newcastle University) for technical support, the genomics core facility for whole exome sequencing (WES), the Bioinformatic support unit (BSU) for initial WES processing. This project was funded by an Investigator Award in Science from the Wellcome Trust (209451) to J.A.V.