Oral anticoagulation and vitamin K deficiency.

A 61-year old woman with atrial fibrillation developed macrohaematuria during anticoagulant treatment with a direct oral factor Xa inhibitor for stroke prevention. Abnormal results of coagulation assays were first interpreted as an effect of the anticoagulant. However, upon further testing diagnosis of vitamin K deficiency was established. After vitamin K supplementation, coagulation tests normalized and macrohaematuria disappeared. Treatment with broad spectrum antibiotics for urinary tract infection was finally established as a rare cause for vitamin K deficiency in the patient.