A 32-year-old man from rural Maharashtra presents with jaundice, dark urine, and abdominal pain for 5 days. He reports consuming contaminated water from a local well 3 weeks ago. On examination, he has hepatomegaly and mild splenomegaly. His liver function tests show ALT 2400 U/L, AST 1800 U/L, total bilirubin 8.2 mg/dL, and INR 1.1. Serum IgM anti-HAV is positive. He has no history of jaundice before. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Acute Hepatitis A ### Key Clinical Features **Key Point:** The patient presents with the classic triad of acute viral hepatitis: jaundice, dark urine (conjugated hyperbilirubinemia), and abdominal pain. The 3-week incubation period following contaminated water exposure is pathognomonic for hepatitis A. ### Serological Confirmation **High-Yield:** IgM anti-HAV positivity is the gold standard for acute hepatitis A diagnosis. This antibody appears early in infection and persists for 4–6 months, making it the definitive marker of acute infection. ### Severity Assessment **Clinical Pearl:** Despite markedly elevated transaminases (ALT 2400, AST 1800), the INR is normal (1.1), indicating preserved synthetic function. This is the hallmark of **uncomplicated acute hepatitis A**. Fulminant liver failure would show INR >1.5 and encephalopathy. ### Why Not Fulminant Failure? **Key Point:** Fulminant hepatic failure in hepatitis A is rare (<0.1% in immunocompetent adults) and presents with: - INR >1.5 (this patient: 1.1) - Encephalopathy (absent here) - Rapid bilirubin rise with falling transaminases (not seen) - Coagulopathy (absent) ### Hepatitis A Epidemiology **Mnemonic: HAV-FECAL** — Hepatitis A Virus spreads via Fecal-Oral route, Enteric transmission, Contaminated food/water, Acute illness, Lifelong immunity after recovery. | Feature | Hepatitis A | Hepatitis B | Hepatitis E | | --- | --- | --- | --- | | Incubation | 2–7 weeks | 6–24 weeks | 2–8 weeks | | Transmission | Fecal-oral | Blood/sexual | Fecal-oral | | Chronicity | Never | 5–10% | Rarely (except pregnancy) | | Fulminant risk | <0.1% | 0.5–1% | 15–25% in pregnancy | | IgM antibody | Diagnostic | Not diagnostic | Diagnostic | ### Prognosis **Clinical Pearl:** Acute hepatitis A in immunocompetent individuals has >99% recovery rate with no chronic sequelae. The patient will develop lifelong immunity.