A 32-year-old man from rural Maharashtra presents with jaundice, dark urine, and clay-coloured stools for 10 days. He reports consuming contaminated water 6 weeks ago. On examination, he is afebrile with mild hepatomegaly and no ascites. Laboratory investigations show: total bilirubin 8.2 mg/dL, ALT 2400 U/L, AST 1800 U/L, ALP 180 U/L, albumin 3.8 g/dL, INR 1.1. Anti-HAV IgM is positive; anti-HEV IgM is negative. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Acute Hepatitis A ### Key Clinical Features **Key Point:** The combination of acute jaundice, dark urine, clay-coloured stools, recent contaminated water exposure, and positive anti-HAV IgM is diagnostic of acute hepatitis A. ### Epidemiological Clues - **Incubation period:** 6 weeks is consistent with HAV (15–50 days) - **Route of transmission:** Fecal-oral route; contaminated water is a classic source in endemic areas like rural India - **Age:** Adults typically present with symptomatic disease ### Laboratory Interpretation | Parameter | Finding | Interpretation | |-----------|---------|----------------| | Anti-HAV IgM | **Positive** | Acute infection (diagnostic) | | Anti-HEV IgM | Negative | Rules out HEV | | ALT/AST | Markedly elevated (>1000) | Hepatocellular necrosis | | Bilirubin | 8.2 mg/dL | Cholestasis component | | Albumin | 3.8 g/dL | Preserved synthetic function | | INR | 1.1 | Normal; no coagulopathy | **High-Yield:** Anti-HAV IgM appears early in acute infection and is the gold standard for diagnosis. It becomes negative within 6 months; anti-HAV IgG persists for lifelong immunity. ### Clinical Course in This Patient **Clinical Pearl:** The preserved albumin and normal INR indicate **fulminant hepatic failure has NOT developed**. This patient has acute hepatitis A with good synthetic function and will likely recover completely without intervention. ### Why HAV (Not HEV) Despite Similar Presentation **Key Point:** Although both HAV and HEV cause acute hepatitis with similar biochemistry, the **positive anti-HAV IgM and negative anti-HEV IgM** make HAV the definitive diagnosis. HEV would show anti-HEV IgM positivity. **Mnemonic: HAV vs HEV in Acute Infection** - **HAV:** Fecal-oral, **shorter incubation (2–7 weeks)**, **no chronicity**, anti-HAV IgM positive - **HEV:** Fecal-oral, **longer incubation (2–9 weeks)**, **can be chronic in immunocompromised**, anti-HEV IgM positive ### Management Approach 1. Supportive care (hydration, rest, nutritional support) 2. Monitor for fulminant hepatic failure (serial INR, bilirubin, encephalopathy) 3. Avoid hepatotoxic drugs 4. No specific antiviral therapy needed 5. Prognosis: ~99% recovery in immunocompetent adults [cite:Harrison 21e Ch 297]