Other less common predisposing factors include Protein S deficiency, Factor V Leiden mutation, Antithrombin III deficiency, Antiphospholipid antibody syndrome (Anticardiolipin antibody) and Lupus anticoagulant.3,13 Several reported cases have however occurred in patients without any of these deficiencies.14,15. This evidence concerns the gene PROS1 and antiphospholipid syndrome.