[Acquired warfarin resistance in a patient with mechanical heart valve]

We present a case report of a 37-year-old man with a mechanical mitral valve, who, presumably because of malabsorption, developed resistance to oral anticoagulant therapy. The patient was then treated with a replacement of the mechanical valve to biological valves, thereby eliminating the need for anticoagulant therapy. Our case report summarises the diagnostic approach to elucidate apparent resistance to anticoagulant therapy.