Antiphospholipid syndrome and factor V Leiden. Three cases with recurrent venous thrombosis.

Recurrent thrombosis is a common complication of various rheumatic disorders and is part of the definition of antiphospholipid syndrome. We report three cases of recurrent venous thrombosis due not only to antiphospholipid syndrome with a normal activated partial thromboplastin time but also to resistance to activated protein C caused by the factor V Leiden mutation. These three cases confirm that thrombotic disease is frequently multifactorial and suggest that resistance to activated protein C should be looked for routinely in patients with suggestive clinical manifestations, particularly when standard clotting tests are normal.