Case studies in therapeutics: warfarin resistance and inefficacy in a man with recurrent thromboembolism, and anticoagulant-associated priapism.

A 52 year-old male unemployed labourer was referred because of recurrent thromboembolism. An episode of thrombophlebitis migrans 3 months earlier had been followed by a pulmonary embolus a week later, and then a deep vein thrombosis despite apparently adequate anticoagulant therapy with warfarin 10 mg daily (INRs between 2 and 4). For 9 years he had suffered from hypertension for which he took lisinopril 2.5 mg daily, had smoked 20 cigarettes daily since his teens and drank 12–15 pints of beer each week. On presentation, his right leg remained hot, swollen and tender to the thigh but there were no other abnormal findings. Investigations revealed a normochromic, normocytic anaemia (Hb 11.6 g dl−1 ) and his erythrocyte sedimentation rate, which had been 11 mm h−1, had risen to 35 mm h−1. Renal and liver function tests, autoantibody screen, and prostate-specific antigen were normal. Antithrombin III, protein C and S concentrations were all within normal limits and ultrasound of the abdomen and pelvis, barium meal and enema, and CT of the thorax, abdomen and pelvis, bronchoscopy and brushings also failed to reveal any abnormality. He was commenced on full-dose (porcine mucosal) heparin for 10 days and the warfarin dose was increased to 15 mg daily until his INR had risen to 4.0, when his plasma warfarin concentration was measured at 3.1 mg l−1.