Summary
A 57 year old man presented with apparently spontaneous lower extremity deep vein
thrombosis and pulmonary embolism. He was treated in conventional fashion with intravenous
heparin and oral warfarin. After 4 daily doses of warfarin the prothrombin and proconvertin
(P+P) time was within therapeutic range, and heparin was stopped. Over the next six
hours complete defibrination occurred, associated with severe bleeding complications.
Functional protein C measured after normalization of routine coagulation tests averaged
40% of normal, and was only 3.5% of normal immediately prior to the episode of defibrination.
We conclude that the very low functional protein C levels seen immediately prior to
defibrination were caused by a combination of pre-existent protein C deficiency and
warfarin therapy, and directly predisposed to defibrination once heparin was stopped,
despite “therapeutic” warfarin anticoagulation. Exacerbation of intravascular coagulation
should be considered a potential prothrombotic effect of warfarin therapy in protein
C deficient individuals.
Keywords
Protein C deficiency - Warfarin therapy - Disseminated intravascular coagulatione
