A 28-year-old male farmer from Tamil Nadu presents with a 5-day history of high-grade fever, severe headache, myalgia, and conjunctival suffusion without exudate. On day 6, he develops jaundice, acute kidney injury (creatinine 3.2 mg/dL), and pulmonary hemorrhage with hemoptysis. Blood culture on day 2 was positive for a thin, motile, aerobic spirochete. What is the most likely diagnosis?

Explanation

## Diagnosis: Weil's Disease (Severe Leptospirosis) ### Clinical Presentation **Key Point:** Weil's disease is the severe, icteric form of leptospirosis caused by *Leptospira interrogans* serovars, typically *L. icterohaemorrhagiae* and *L. copacabana*. The patient presents with the classic biphasic course: 1. **Leptospiremic phase (days 1–7):** High fever, headache, myalgia, conjunctival suffusion (hallmark finding — injection without exudate) 2. **Immune phase (after day 7):** Jaundice, renal failure, pulmonary hemorrhage, bleeding manifestations ### Pathognomonic Features | Feature | Significance | |---------|-------------| | **Conjunctival suffusion** | Pathognomonic for leptospirosis; NO exudate (unlike bacterial conjunctivitis) | | **Jaundice + AKI + pulmonary hemorrhage** | Classic triad of Weil's disease | | **Occupational exposure** | Farmer in endemic region (Tamil Nadu); contact with rodent urine | | **Thin, motile spirochete on blood culture** | *Leptospira* morphology; positive in first week | ### Microbiology **High-Yield:** *Leptospira* are thin (0.1 μm × 6–20 μm), aerobic spirochetes with hook-shaped ends. They are cultured on Fletcher's or EMJH medium (selective, enriched). Blood culture is positive during the leptospiremic phase (first 7–10 days); urine culture becomes positive after day 10. ### Diagnostic Confirmation - **Microscopic agglutination test (MAT):** Gold standard; paired sera showing ≥4-fold rise in titer confirms diagnosis - **PCR:** Rapid, sensitive during first week - **IgM ELISA:** Positive by day 5–7 ### Management **Clinical Pearl:** Early treatment with doxycycline (100 mg BD × 7 days) or penicillin G (6 MU IV 6-hourly × 7 days) reduces severity and duration. In severe disease (Weil's), IV penicillin or ceftriaxone is preferred. **Mnemonic for Weil's disease triad:** **JAP** — **J**aundice, **A**cute kidney injury, **P**ulmonary hemorrhage. ### Epidemiology in India **Key Point:** Leptospirosis is endemic in South India (Tamil Nadu, Kerala, Karnataka), especially during monsoon. Occupational exposure (farmers, slaughterhouse workers, sewage workers) and contact with contaminated water are risk factors. [cite:Park 26e Ch 8]