Delayed Vesicular Urticarial Dermatosis Due to Apixaban.

Cutaneous adverse drug reactions (cADR) are delayed hypersensitivity reactions that are T-cell mediated. Novel oral anticoagulants, including Factor Xa inhibitors, are increasingly used as therapeutic or prophylactic management of thrombosis and atrial fibrillation. We introduce the case of a 78-year-old woman with no known allergies and a history of atrial fibrillation who was started on apixaban for cerebrovascular accident prophylaxis. Approximately nine days after starting apixaban, she developed a vesicular-urticated erythematous rash initially located on her right upper extremity, progressing to her face. She was evaluated after two weeks for the persistence of symptoms and improved with hydroxyzine and prednisone. Subsequently, she was advised to discontinue and evade all Factor Xa inhibitors, including apixaban, and was switched to warfarin. Naranjo score scale was 5-6. The patient declined skin biopsy and drug challenge. After a month of discontinuation of systemic steroids, patch testing was performed with apixaban, rivaroxaban, and edoxaban, with a negative result. Since this episode, the patient has not had a recurrence of the rash. As far as we know, this is the first case report of a non-severe cADR to apixaban. Even though there are no standardized protocols for diagnosing drug reactions to Factor Xa inhibitors, patch testing at increasing non-irritant concentrations with re-challenge of alternative agents and the suspected offending agent, if possible, should be included in the evaluation of a cADR.