A 30-year-old woman presents with severe hemolytic anemia (Hb 5.8 g/dL), thrombocytopenia, renal failure, and confusion after a diarrheal illness. Peripheral smear shows schistocytes. ADAMTS13 activity is 80% (normal). Stool cultures grow Shiga toxin-producing E. coli (STEC, O157:H7). What is the definitive treatment?
- A Therapeutic plasma exchange (TPE) to remove ADAMTS13 antibodies
- B Eculizumab (complement C5 inhibitor)
- C Supportive care: dialysis, transfusions, avoid antibiotics ✓
- D Rituximab to suppress autoantibody production
Correct answer: C. Supportive care: dialysis, transfusions, avoid antibiotics
Explanation
This is Shiga toxin-associated HUS (STEC-HUS), not thrombotic thrombocytopenic purpura (TTP). ADAMTS13 activity >10% effectively rules out TTP (where it is <10%). STEC-HUS is managed with supportive care: dialysis for renal failure, red cell transfusions for anemia, and avoidance of antibiotics (which may lyse bacteria and release more toxin, worsening the syndrome). TPE and rituximab are treatments for TTP (autoimmune ADAMTS13 deficiency). Eculizumab is used in atypical HUS (complement-mediated) but not STEC-HUS.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.