A 28-year-old woman presents to the emergency department with a 2-day history of fatigue, fever, and confusion. She reports feeling increasingly weak and has noticed small red spots (petechiae) on her legs. She denies any recent trauma, significant bleeding, or diarrhea. Her medical history is unremarkable except for a mild viral upper respiratory infection two weeks ago, which resolved without treatment. On physical examination, she appears pale and mildly jaundiced. Neurological examination reveals disorientation but no focal deficits. Laboratory results reveal a hemoglobin of 8 g/dL (normal: 12–16 g/dL), platelet count of 15,000/µL (normal: 150,000–450,000/µL), and elevated lactate dehydrogenase (LDH) at 1,200 U/L (normal: 140–280 U/L). A peripheral blood smear shows schistocytes (fragmented red blood cells). Coagulation studies (PT, INR, fibrinogen) are within normal limits, and renal function is mildly impaired with a creatinine of 1.5 mg/dL (normal: 0.6–1.2 mg/dL). What is the most likely diagnosis for this patient?
