1. From the Department of Pediatrics (S.K., L.M., P.M.), Thrombosis Program, Stollery Children’s Hospital, Edmonton, Alberta, Canada; Department of Pediatrics (M. Andrew, deceased), Division of Hematology, Hospital for Sick Children, Toronto Ontario, Canada; Department of Pediatrics (A.K.C.), Division of Hematology, Children’s Hospital at Chedoke McMaster, Hamilton, Ontario, Canada; and Department of Pediatrics (M. Adams, G.d.), Division of Neurology, Hospital for Sick Children, Toronto, Ontario, Canada.