1 INTRODUCTION Human coagulation factor X deficiency is a very rare autosomal recessive condition affecting between 1 in 500,000 and 1 in 2 million people. The deficiency is caused by F10 gene mutations on chromosome 13. The condition is characterised by spontaneous bleeding, which can be life-threatening.1, 2 Historically, such bleeds have been treated with fresh-frozen plasma or prothrombin complex concentrates (PCC).