A 32-year-old man from rural Bihar presents with jaundice, dark urine, and pale stools for 10 days. He reports consuming contaminated water 6 weeks ago. On examination, he is afebrile, icteric, with hepatomegaly but no splenomegaly. Liver function tests show ALT 2800 IU/L, AST 2200 IU/L, bilirubin 8.5 mg/dL (direct 6.2 mg/dL), albumin 3.8 g/dL, PT 12 seconds. 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 positive anti-HAV IgM in the context of acute hepatitis with a clear exposure history (contaminated water 6 weeks prior) confirms acute hepatitis A infection. ### Incubation Period and Timeline - **Incubation period of HAV:** 15–50 days (mean 28–30 days) - Patient's exposure 6 weeks ago fits perfectly with current presentation - Anti-HAV IgM appears early in infection and persists for ~6 months ### Laboratory Interpretation | Parameter | Finding | Significance | |-----------|---------|---------------| | ALT/AST | Markedly elevated (>2000) | Typical of acute viral hepatitis | | Bilirubin | 8.5 mg/dL (predominantly direct) | Cholestatic phase of acute hepatitis | | Albumin | 3.8 g/dL (near-normal) | Preserved synthetic function | | PT | 12 seconds (normal) | No coagulopathy; good prognosis | | Anti-HAV IgM | **Positive** | Diagnostic of acute HAV | | Anti-HEV IgM | Negative | Rules out acute HEV | ### Clinical Pearl **Clinical Pearl:** Acute hepatitis A in adults typically presents with more severe symptoms than in children, but prognosis remains excellent with fulminant hepatic failure occurring in <1% of cases. The preserved PT and albumin indicate good hepatic reserve. ### High-Yield Facts **High-Yield:** - HAV is transmitted via fecal-oral route; contaminated water is a classic source in endemic areas - No chronic carrier state exists for HAV - Anti-HAV IgM is the diagnostic test of choice in acute infection - Recovery is complete in >99% of immunocompetent adults [cite:Harrison 21e Ch 297]