1 Van Creveld kliniek, University Medical Center Utrecht, Utrecht, The Netherlands.
2 Lund University, Dept. of Clinical Sciences Lund, Paediatrics, Lund, Sweden; Skåne University Hospital, Department of Paediatrics and Malmö Centre for Thrombosis and Haemostasis, Malmö, Sweden. Electronic address: Rolf.Ljung@med.lu.se.