[Secondary resistance to coumarin derivatives in a patient with a hypercoagulability syndrome]

A 23-year-old woman with deep (leg) vein thrombosis was hospitalised because the Quick value had not decreased despite administration of phenprocoumon. Two years previously she had sustained an anterior wall myocardial infarction and a scar on her right kidney had been an incidental sonographic finding. There was bluish, fine reticular discoloration over the toes of both legs. Physical examination was otherwise unremarkable except for obesity.

The concentration of creatine kinase was raised to 250 U/l and that of lactate dehydrogenase to 300 U/l. The platelet count was decreased to 75/nl. The level of IgG anti-cardiolipin antibodies was raised (204 U/l) and the test for lupus anticoagulant positive. A biopsy of the skin from a toe revealing livedoid vasculitis, primary antiphospholipid syndrome (PAPS) was diagnosed.

Noncompliance, excessive vitamin K ingestion, drug interaction and malabsorption were excluded as cause of the lacking action of phenprocoumon. Despite anti-coagulation with high-dosage low-molecular heparin and inhibition of platelet aggregation with ticlopidine and finally also immunosuppressive treatment with cyclophosphamide, skin necroses developed on the toes and she had recurrent pulmonary embolisms of which she died.

Standard treatment of PAPS is effective anti-coagulation with coumarin derivatives. Secondary resistance to coumarin is a rare occurrence: its cause remains unknown.