A 2-year-old boy presents with pallor, decreased urine output, and petechiae 5 days after an episode of bloody diarrhea. Hemoglobin is 6.8 g/dL, platelets 45,000/mm3, creatinine 2.4 mg/dL, and the peripheral smear shows fragmented red cells. The causative agent acts through which mechanism?

• A Direct invasion of glomerular endothelium by bacteria
• B Anti-neutrophil cytoplasmic antibody mediated capillaritis
• C Immune complex deposition activating classical complement pathway
• D Toxin-mediated endothelial injury causing platelet-rich microthrombi ✓

Explanation

This is typical diarrhea-associated hemolytic uremic syndrome, the commonest cause of acute kidney injury in young children, caused by Shiga toxin producing E. coli O157:H7. Shiga toxin injures glomerular endothelial cells, triggering platelet aggregation and microangiopathic hemolytic anemia, thrombocytopenia and AKI. Immune complex mediated disease such as post-streptococcal glomerulonephritis produces low complement rather than schistocytes and thrombocytopenia.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.