A 4-year-old boy is brought to the emergency department by his parents with complaints of fatigue, decreased urine output, and dark-colored urine for the past 24 hours. The parents report that the child had an episode of bloody diarrhea five days ago, which they initially attributed to food poisoning after eating undercooked hamburgers at a family barbecue. The diarrhea has since resolved, but the child has become lethargic and pale. History: Past Medical History: Unremarkable Medications: None Family History: No history of kidney disease or clotting disorders Social History: Attends daycare Physical Examination: General: Pale, lethargic child Vital Signs: Temperature: 37.5°C Blood Pressure: 135/90 mmHg (elevated) Heart Rate: 110 bpm Skin: Petechiae on the lower limbs Abdomen: Mild tenderness with no hepatosplenomegaly Edema: Mild periorbital swelling Neurological: Alert but fatigued, no focal deficits Initial Laboratory Findings: CBC: Hemoglobin: 7.8 g/dL (low) Platelets: 60,000/µL (low) Peripheral smear: Schistocytes present (fragmented RBCs) Creatinine: 2.1 mg/dL (elevated) BUN: 40 mg/dL (elevated) Urinalysis: Hematuria, proteinuria Stool culture: Pending, but preliminary report shows gram-negative rods LDH: Elevated Haptoglobin: Low Coombs test: Negative What is the most likely diagnosis in this patient?

A 42-year-old woman presents to the emergency department with a 24-hour history of weakness, fever, and intermittent seizures. She reports feeling increasingly fatigued over the past week and has noticed easy bruising and dark urine. She denies any recent diarrhea, abdominal pain, or bleeding. Her medical history is unremarkable, and she is not taking any medications. On physical examination, she appears pale and mildly jaundiced. Neurological examination reveals disorientation and focal neurological deficits during seizure episodes. Laboratory results reveal a hemoglobin of 7.5 g/dL (normal: 12–16 g/dL), platelet count of 10,000/µL (normal: 150,000–450,000/µL), creatinine of 1.5 mg/dL (normal: 0.6–1.2 mg/dL), and elevated lactate dehydrogenase (LDH) at 800 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. What is the primary pathophysiological mechanism underlying her condition?

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?

A 5-year-old boy is admitted to the pediatric ICU for severe iron overdose after ingesting a large quantity of his mother’s ferrous sulfate tablets. He initially presented with vomiting, diarrhea, abdominal pain, and metabolic acidosis. His serum iron level was 650 mcg/dL (normal: 50-150 mcg/dL). He was started on intravenous deferoxamine therapy, which has been continued for the past 30 hours. Over the past few hours, he has developed progressive respiratory distress, requiring increased oxygen support. Chest X-ray shows bilateral pulmonary infiltrates with no evidence of cardiomegaly or pleural effusions. Question: What is the most likely cause of this patient’s new-onset respiratory symptoms?

A 3-year-old girl is brought to the emergency department after being found with an open bottle of iron supplements that belonged to her mother. The mother estimates that the child may have ingested multiple pills. The child is irritable and vomiting and has abdominal pain. Her vitals are: • Temperature: 37.8°C (100°F) • Heart rate: 140/min • Blood pressure: 85/50 mmHg Laboratory results: • Arterial pH: 7.30 • Anion gap: 20 • Serum iron level: 450 mcg/dL (normal: 50–150 mcg/dL) • Glucose: 65 mg/dL An abdominal X-ray shows multiple radiopaque pills in the stomach and intestines. Question: Which of the following is the most appropriate initial treatment for this patient?

A 48-year-old male with a history of severe pancreatitis and recent abdominal trauma is admitted to the ICU. Over the past several hours, he has developed worsening tachycardia, hypotension, and respiratory distress. On examination, his abdomen is tense and distended with decreased bowel sounds. Bedside ultrasonography reveals elevated intra-abdominal pressure (IAP) > 25 mmHg. Arterial blood gas shows respiratory acidosis and hypoxia. Question: Which of the following is the most likely consequence of this patient’s condition?