A 3-year-old boy develops pallor and decreased urine output five days after an episode of bloody diarrhea. Hb is 6.5 g/dL, platelet count 25,000/uL, creatinine 2.1 mg/dL. Peripheral smear shows helmet cells and fragmented red cells with no fever at onset. The toxin responsible acts primarily by:

• A Direct cytotoxic effect on renal tubular epithelium
• B Causing ADAMTS13 deficiency through autoimmune destruction
• C Inducing IgA deposition in glomerular capillaries
• D Inactivating elongation factor leading to endothelial injury and platelet activation ✓

Explanation

Shiga toxin from EHEC O157:H7 enters glomerular endothelial cells, inhibits the 60S ribosomal subunit via its action on elongation factors, and triggers endothelial injury, tissue factor release, and platelet-rich microthrombi. The resulting microangiopathic hemolytic anemia with schistocytes, thrombocytopenia, and acute kidney injury defines typical hemolytic uremic syndrome. ADAMTS13 deficiency characterizes thrombotic thrombocytopenic purpura, which typically has prominent neurological features rather than preceding bloody diarrhea.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.