Case 2: Diarrhea and Petechiae in an 8-year-old Girl

A previously healthy 8-year-old girl is referred to the emergency department for acute-onset diarrhea with abdominal pain. This illness began 2 days earlier with coryza, nonproductive cough, and subjective fever, for which she took ibuprofen. She denies a change in urine output, mental status changes, headache, nausea, and emesis. She has not had recent travel. Her only home medication is a fiber supplement for chronic constipation. All immunizations are up to date except for the annual influenza vaccine.In the emergency department, her temperature is 104.2°F (40.1°C), heart rate is 77 beats/min, respiratory rate is 27 breaths/min, and oxygen saturation is 99% on room air. She was hypertensive, with a blood pressure of 117/81 mm Hg. She is pale, alert, cooperative, and not toxic-appearing. There is no periorbital edema or tonsillar enlargement, but palatine petechiae are present. Respirations are clear and unlabored. She is in regular rhythm without murmurs or gallops. Her abdomen is soft and nondistended, with normoactive bowel sounds. She is mildly tender in the right upper quadrant. She has a significant number of pretibial petechiae extending to the dorsa of her feet, and she demonstrates appropriate strength and muscle tone, with normal reflexes throughout.Initial laboratory findings are significant for creatinine level, 1.12 mg/dL (99.01 μmol/L); hematocrit level, 28%; platelet count, 9×103/μL (9×109/L); and white blood cell count, 4,200/μL (4.2×109/L). Further laboratory and infectious evaluations reveal the cause of her illness.Soon after admission, the patient develops gross hematuria and worsening renal function. Hematologic evaluation reveals reticulocyte index, 0.4; lactate dehydrogenase level, 2,969 U/L (49.6 μkat/L); and total bilirubin level, 5.7 mg/dL (97.5 μmol/L). Schistocytes are seen on peripheral blood smear. Additional laboratory tests show alanine aminotransferase level, 308 U/L (5.1 μkat/L); aspartate aminotransferase level, 929 U/L (15.5 μkat/L); prothrombin time, 15.8 seconds; international normalized ratio, 1.4; activated partial thromboplastin time, 37.9 seconds; and fibrinogen level, 0.0132 mg/dL (