Severe Leptospirosis with Apyrexia and an Atypical Presentation: Rapid Progression to Multi-Organ Failure.

Introduction: Leptospirosis is a common zoonotic infection in tropical regions with diverse clinical manifestations. Fever occurs in 89-100% of cases, while afebrile cases are extremely rare and seldom reported in the literature, accounting for less 1% of severe leptospirosis cases, posing a diagnostic challenge in clinical practice. Case description: we report on a 43-year-old male farmer from northern Vietnam who was admitted with rapidly progressive jaundice and severe acute kidney injury following exposure to contaminated paddy field water. Notably, the patient remained afebrile throughout the disease course - an atypical presentation rarely seen in severe leptospirosis. The incubation period was extremely short (one day) with rapid progression to multi-organ failure within three days. Diagnosis was confirmed serologically with Leptospira IgM >100 U/ml and a more than 4-fold increase in IgG titre (from 10.4 to 72.3 U/ml) according to WHO criteria. The SOFA score at admission was 9 points. The patient responded well to combination antibiotic therapy, corticosteroids and renal replacement therapy, achieving complete recovery after 24 days. Conclusion: This case emphasises the importance of not excluding leptospirosis even in the absence of fever, particularly in endemic areas with occupational risk factors. Markedly elevated bilirubin disproportionate to AST, ALT and rapidly progressive acute kidney injury are important suggestive signs. LEARNING POINTS: Distinguish between fever syndrome (systemic inflammatory symptoms) and pyrexia (elevated body temperature) - patients can have severe infections with fever syndrome but normal body temperature.A national early warning score (NEWS2) based on vital signs may fail to capture disease severity in afebrile presentations, while sequential organ failure assessment (SOFA) scores provide better risk stratification.Recognise the diagnostic pattern in severe leptospirosis: markedly elevated bilirubin (>580 μmol/l) with disproportionately mild liver enzyme elevation (AST <200 U/l) combined with rapidly progressive acute kidney injury.