Question of the week. A 73-year-old woman with a history of hy | Daily Medical Info 4 Medics

Question of the week.
A 73-year-old woman with a history of hypertension and chronic obstructive pulmonary disease presents to the emergency department with red streaking on her right arm.
She grazed the arm 2 days ago and stopped minimal bleeding from the wound by applying local pressure. She reports a fever of 38.7°C.

She has a platelet count of 243,000 per mm³ (reference range, 150,000–350,000). She is started on intravenous vancomycin and ceftriaxone. She is then hospitalized, improves quickly, and is discharged on day 3.

Five days after discharge, the patient notices a petechial rash on her legs and presents again for evaluation.
A complete blood count reveals these results: hemoglobin 11.4 g/dL (reference range, 12.0–16.0), leukocytes 4200 per mm³ (4500–11,000), platelets 18,000 per mm³ (150,000–350,000), and a normal fibrinogen level.

Review of the peripheral-blood smear reveals marked reduction of the platelet count, but normal platelet morphology. No schistocytes are present.