Footnotes

• Funding MMR is grateful to the Medical Research Council (MRC MR/S005021/1), the National Institutes of Neurological Diseases and Stroke and the office of Rare Diseases (U54NS065712) and to the Muscular Dystrophy Association (MDA510281) for their support. The INC (U54NS065712) is part of the NCATS Rare Diseases Clinical Research Network (RDCRN). MMR and ARs research is also supported by the National Institute for Health Research University College London Hospitals Biomedical Research Centre.

• Competing interests None declared.

• Patient consent for publication Not required.

• Provenance and peer review Commissioned; externally peer reviewed.

• Data availability statement No data are available.