Abstract
We occasionally experience that healthy children show a transient high levels of anticoagulants
after infection． Most of their features are subclinical or rarely hemorrhagic/thrombotic symptom， and they
spontaneously recover from them． Thrombosis is caused by anticoagulants in patients with anti-phospholipid
antibody syndrome， and the anticoagulant positive children tend to be easy bleeding． It was reported that low
activity of complement and anticoagulant factor were complicated in acute phase， yet there was no certain
tendency or fixed mechanism． We experienced three pediatric cases with hemorrhage and anticoagulants positive．
Case l：2-y-o boy with lupus anticoagulant（LAC）， anti－cardiolipin antibody（ACA）and low factor VIII，factor
IX activity． Case 2：2-y-o girl with LAC， ACA and low factor IX activity． Case 3：4-y-o girl with LAC and low
Factor IX activity． All cases showed low complement activity， instead of anti-nuclear antibody negative， and they
clinically improved in a natural course． Case 2 and 3 also clinically and serologically improved． We concluded
that both of the anti-phospholipid antibodies and the coagulation inhibitors influence the hemorrhagic symptoms
during active phase．
