A 35-year-old rice-field worker from Tamil Nadu develops fever, jaundice, haematuria, and acute kidney injury. Serum creatinine is 5.2 mg/dL. Blood culture in EMJH medium is positive. Microscopic agglutination test (MAT) titre is ≥1:400 against Leptospira interrogans. The pathological mechanism of acute tubular injury in leptospirosis involves:
- A Direct tubular invasion by spirochaetes and lipopolysaccharide-mediated proximal tubular injury ✓
- B Immune complex deposition in tubular basement membrane
- C Aflatoxin-mediated mitochondrial dysfunction in tubular cells
- D Hypovolaemia alone secondary to hepatic failure
Explanation
Leptospirosis causes acute interstitial nephritis and renal tubular necrosis by direct invasion of the tubular epithelium (leptospires are found in renal tubules on autopsy) and by the action of leptospiral lipopolysaccharide, outer membrane proteins (OmpL1), and haemolysins (sphingomyelinase) that disrupt tubular cell membranes, cause oxidative injury, and trigger TLR2/TLR4-mediated pro-inflammatory cytokine release. The kidney is the primary target organ even in anicteric leptospirosis. Weil's disease (severe leptospirosis) combines hepatic failure + AKI + haemorrhage. Immune complex nephritis occurs in some cases but direct toxicity is the primary mechanism. MAT is the gold standard serological test.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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