Protein S (PS) deficiency, an autosomal dominant hereditary thrombophilia, is more prevalent in East Asian populations than in\nCaucasians. PS-deficient patients have historically been administered a heparin product followed by warfarin for the treatment\nand secondary prevention of venous thromboembolism (VTE). However, warfarin can be ineffective or causes detrimental effects\nin rare cases. While direct oral anticoagulants (DOACs) are being increasingly used for the treatment and prevention of VTE, their\nefficacy in PS-deficient patients has not been established. We describe a 91-year-old woman who presented with chronic bilateral\nlower leg swelling with VTE that was refractory to warfarin anticoagulation therapy for over 1 year. Her recurrent VTE was\ndiagnosed as quantitative hereditary PS deficiency. Rivaroxaban was administered as maintenance therapy instead of warfarin;\nafter 8 weeks, the severities of the patient�s leg swelling and venous ulcerations were significantly reduced with rivaroxaban\ncompared to warfarin, thus demonstrating the efficacy of rivaroxaban for warfarin-refractory chronic VTE associated with\nhereditary PS deficiency. This case illustrates that rivaroxaban can potentially serve as therapeutic agents to treat warfarinrefractory\nVTE in PS-deficient patients. Further investigations are required to confirm the efficacy of rivaroxaban on the long term\nin this regard.
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