1 Centre for Neuromuscular Diseases, National Hospital for Neurology and Neurosurgery, University College London Hospital, London, UK; Department of Neuromuscular Disease, Institute of Neurology, University College London, London, UK.
2 Department of Haematology, University College London Hospital, London NW1 2BU, UK.
3 Department of Histopathology, University College London Hospital, London NW1 2BU, UK.
4 Department of Rheumatology, University College London Hospital, London NW1 2BU, UK.
5 Department of Dermatology, University College London Hospital, London NW1 2BU, UK.
6 Department of Rheumatology, Sheffield University Hospital, Sheffield, UK.
7 Department of Rheumatology, University College London Hospital, London NW1 2BU, UK. Electronic address: [email protected].