A 28-year-old man from rural Maharashtra presents with jaundice, dark urine, and abdominal pain for 10 days. He reports consuming contaminated water from a local well 4 weeks ago. On examination, he has hepatomegaly and mild splenomegaly. Liver function tests show ALT 1200 U/L, AST 980 U/L, alkaline phosphatase 180 U/L, and total bilirubin 8.2 mg/dL. Anti-HAV IgM is positive; anti-HAV IgG is negative. Prothrombin time is normal. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Acute Hepatitis A ### Key Clinical Features **Key Point:** The combination of acute jaundice, dark urine, hepatomegaly, and a clear exposure history (contaminated water 4 weeks prior) points to acute viral hepatitis with a fecal-oral route of transmission. ### Serological Interpretation **High-Yield:** Anti-HAV IgM positivity is the gold standard marker for acute hepatitis A infection. IgM antibodies appear early in infection and persist for 3–6 months, making them diagnostic of acute infection. The absence of anti-HAV IgG (which appears later and confers lifelong immunity) confirms this is a primary infection, not past exposure. ### Epidemiological Clues **Clinical Pearl:** Hepatitis A is endemic in rural India due to poor sanitation. Waterborne transmission following consumption of contaminated water is the classic exposure history. The incubation period of 15–50 days (average 28–30 days) matches the 4-week timeline in this case. ### Laboratory Pattern **Key Point:** Marked elevation of transaminases (ALT > AST, typically >1000 U/L) with relatively mild elevation of alkaline phosphatase is typical of acute hepatitis A. Normal prothrombin time rules out fulminant hepatic failure, which is rare in HAV unless the patient is elderly or has underlying liver disease. ### Comparison with Other Hepatitis Viruses | Feature | Hepatitis A | Hepatitis E | Hepatitis B | Hepatitis C | | --- | --- | --- | --- | --- | | **Route** | Fecal-oral | Fecal-oral (waterborne) | Blood, sexual, vertical | Blood transfusion, IVDU | | **Acute IgM** | Anti-HAV IgM | Anti-HEV IgM | HBsAg, anti-HBc IgM | Anti-HCV (late) | | **Chronicity** | Never chronic | Rarely chronic | 90% chronic (neonates) | 85% chronic | | **Fulminant Risk** | <1% (except elderly) | 1–3% (15–25% in pregnancy) | <1% | Rare | | **Prognosis** | Excellent recovery | Good (poor in pregnancy) | Variable | Often asymptomatic | ### Why This Is Acute HAV, Not Acute HEV While both are waterborne and endemic in rural India, **anti-HAV IgM is specific for HAV**. HEV would show anti-HEV IgM. Additionally, HEV causes more severe disease in pregnant women and has a higher fulminant rate; this patient is a young man with normal PT, favoring HAV. ### Management Implications **Key Point:** Acute hepatitis A is self-limiting in immunocompetent individuals. Management is supportive (rest, hydration, avoidance of hepatotoxins). No antiviral therapy is needed. Contacts should receive HAV vaccination if seronegative.