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A 62-year-old woman presents with epistaxis from the right nostril. The nosebleed has lasted about 90 minutes, and she has become alarmed by the amount of blood on the tissues and washcloth she has applied to her nose. She denies headache, sinusitis, facial pain, diplopia, and chronic rhinorrhea.
She has had a mild upper respiratory tract infection (URTI), from which she is recovering, but otherwise she was previously in good health. At her annual physical examination 2 weeks earlier, new, mild hypertension (142/90 mm Hg) was diagnosed; lisinopril and low-dose aspirin (ASA) were prescribed. Since she did not have “baby” ASA at home, she has been using standard adult tablets instead.
She has had 3 children by vaginal delivery, extractions of permanent teeth, and a cholecystectomy—all without abnormal bleeding. She has no symptoms of heart failure.
Heart rate is 90 beats per minute and blood pressure, 150/96 mm Hg. Examination of the head, eyes, ears, nose, and throat reveals no sign of any cranial neuropathy. There are bruises on the dorsum of the patient’s right hand and on her left shin, but all other physical findings are normal.
LABORATORY RESULTS ON ADMISSION
Hemoglobin level is 13 g/dL; white blood cell count and platelet count are normal. A chemistry panel and ECG are normal as well. Prothrombin time (PT) and partial thromboplastin time (PTT) are normal; a template bleeding time is 6.5 minutes (normal, 2 to 7 minutes).
Which of the following is most likely responsible for this patient’s epistaxis?