[Serious bleeding complications caused by warfarin with international normalized ratio 2.1].

The risk of bleeding due to anticoagulation therapy with warfarin rises exponentially, when the international normalized ratio (INR) exceeds 4.5. We present a 52-year-old male admitted to the hospital with severe bleeding in the lower limbs caused by warfarin. Laboratory tests showed therapeutic INR (2.1), however the activated partial tromboplastin time was unusually prolonged (135 sec.) and a severe, reversible reduction in factor IX was detected. These findings were suggestive of a mutation in the factor IX propeptide, but thrombocytopathy induced by selective serotonin re-uptake inhibitors could have worsened the bleeding.