A 5-year-old child presents with bloody diarrhoea, fever, and on day 5 develops oliguria, thrombocytopenia, and haemolytic anaemia (peripheral smear: schistocytes). The causative organism and mechanism of renal injury is BEST described by:
- A Shigella dysenteriae type 1 producing Shiga toxin causing direct glomerular endothelial injury
- B Enteroaggregative E. coli producing heat-stable toxin causing HUS
- C Campylobacter jejuni causing post-infectious TTP via molecular mimicry
- D Enterohaemorrhagic E. coli (EHEC, O157:H7) producing Shiga toxin-1/2 absorbed systemically causing haemolytic uraemic syndrome ✓
Explanation
Haemolytic uraemic syndrome (HUS) in children is most commonly caused by EHEC (particularly O157:H7) which produces Shiga toxin 2 (Stx2 being more nephrotoxic than Stx1). Stx is absorbed from the gut, binds to Gb3 receptors on renal glomerular endothelium and mesangial cells, causing protein synthesis inhibition, endothelial apoptosis, microvascular thrombosis, and the triad of MAHA, thrombocytopenia, and AKI (HUS). S. dysenteriae type 1 also produces Shiga toxin and can cause HUS but EHEC O157:H7 is the predominant cause of sporadic HUS in children in most guidelines.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.