The frequency of inherited and acquired prethrombotic disorders in 30 consecutive children with arterial ischemic stroke (AIS) and 10 with sinovenous thrombosis (SVT) was determined at the Hopital de Pediatria, Buenos Aires, Argentina. The median age for AIS was 7.3 years (range, 0.4-18); for SVT it was 6 years (range, 0.8-12.6). Risk factors and underlying disease included infection, dehydration, head trauma, Moyamoya, and lupus. Hemostatic assays included protein C, protein S, antithrombin, plasminogen, activated protein C resistance, factor V Leiden mutation, and antiphospholipid antibodies. Nine children (30%) with AIS had one or more prethrombotic disorders (inherited protein S deficiency (2), inherited protein C deficiency (1), acquired antithrombin deficiency (2), antiphospholipid antibodies (3), and antiphospholipid antibodies and plasminogen deficiency (1). Five children (50%) with SVT tested positive: 1 had inherited protein S deficiency, 3 had acquired antithrombin deficiency, and 1 had antiphospholipid antibodies. No cases of activated protein C resistance or factor V Leiden mutation were found. 
COMMENT. The majority of children with cerebral thrombosis and stroke have underlying disease or risk factors and hereditary or acquired prethrombotic disorders. A complete hemostatic evaluation is recommended for all children with arterial ischemic stroke and sinovenous thrombosis, including those with obvious clinical risk factors.