A 32-year-old man from Delhi presents with jaundice, dark urine, and abdominal pain for 10 days. He reports consuming contaminated water during a recent trip to a rural area 3 weeks ago. On examination, he is icteric with hepatomegaly. Laboratory investigations show: ALT 2800 IU/L, AST 2200 IU/L, alkaline phosphatase 180 IU/L, total bilirubin 8.2 mg/dL, direct bilirubin 6.8 mg/dL, INR 1.2. Serological testing reveals anti-HAV IgM positive, anti-HAV IgG negative. What is the most likely diagnosis?

Explanation

## Diagnosis: Acute Hepatitis A ### Clinical Presentation The patient presents with the classic triad of acute viral hepatitis: jaundice, dark urine (conjugated hyperbilirubinemia), and right upper quadrant pain. The epidemiological clue—contaminated water exposure 3 weeks prior—strongly suggests a fecal-oral transmitted virus. ### Serological Interpretation | Marker | Result | Interpretation | |--------|--------|----------------| | Anti-HAV IgM | Positive | **Acute infection** — indicates current/recent HAV | | Anti-HAV IgG | Negative | No prior immunity; first exposure | | INR 1.2 | Normal | Preserved synthetic function; not fulminant | **Key Point:** Anti-HAV IgM is the diagnostic gold standard for acute hepatitis A. Its presence indicates active viral replication and acute infection, regardless of IgG status. ### Biochemical Pattern - **Markedly elevated transaminases** (ALT > AST): typical of acute viral hepatitis, reflecting hepatocellular necrosis. - **Mild-to-moderate alkaline phosphatase elevation**: cholestasis component but not obstructive pattern. - **Conjugated hyperbilirubinemia** (direct 6.8 mg/dL): hepatocellular dysfunction with impaired excretion. - **Normal INR**: synthetic function preserved; no evidence of fulminant failure. ### Epidemiology & Natural History **High-Yield:** Hepatitis A is transmitted via fecal-oral route; contaminated water is the classic exposure in endemic areas (India, Southeast Asia). Incubation period is 15–50 days (average 28–30 days), consistent with this patient's 3-week timeline. **Clinical Pearl:** Hepatitis A is **self-limited**; 95% of immunocompetent adults recover completely within 6 months without chronic sequelae. No chronic carrier state exists. ### Why INR is Normal Unlike fulminant hepatitis (INR > 1.5), this patient has preserved synthetic function, indicating acute hepatitis without liver failure. ## Pathology Snapshot - **Acute inflammation**: portal and lobular infiltration with lymphocytes and macrophages. - **Hepatocellular necrosis**: spotty (focal) and bridging necrosis in severe cases. - **Cholestasis**: bile plugs in canaliculi; minimal fibrosis (no cirrhosis). - **Recovery**: complete restitution of architecture in survivors [cite:Robbins 10e Ch 20].