1 Centre for Thrombosis, Guy's and St Thomas' NHS Foundation Trust, London, UK; Department of Rheumatology, Copenhagen University Hospital, Copenhagen, Denmark. Electronic address: Karen.schreiber@gstt.nhs.uk.
2 1st Medical Department, University Medical Centre Mannheim, Medical Faculty Mannheim, University of Heidelberg, Germany.
3 Department of Clinical and Biological Sciences, Center of Research of Immunopathology and Rare Diseases - Coordinating Center of the Network for Rare Diseases of Piedmont and Aosta Valley, San Giovanni Hospital, University of Turin, piazza del donatore di Sangue 3, 10054 Turin, Italy.