A 48-year-old man with a 15-year history of alcohol use disorder presents with jaundice, ascites, and spider angiomas. He reports a 2-week illness with fever, malaise, and right upper quadrant pain. Laboratory findings: total bilirubin 9.5 mg/dL, AST 320 IU/L, ALT 180 IU/L, alkaline phosphatase 240 IU/L, INR 1.8, albumin 2.9 g/dL, platelet count 85,000/μL. HBsAg is positive, anti-HBc is positive, anti-HBs is negative. Anti-HAV IgM is negative. HCV antibody is negative. HBV DNA PCR is 8.5 × 10^6 copies/mL. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Acute-on-Chronic Hepatitis B with Decompensated Cirrhosis ### Diagnostic Framework **Key Point:** The presence of **HBsAg positivity with high HBV DNA (8.5 × 10^6 copies/mL)**, combined with clinical and biochemical evidence of **decompensated cirrhosis** (ascites, spider angiomas, elevated INR 1.8, low albumin 2.9 g/dL, thrombocytopenia), indicates **acute-on-chronic hepatitis B** — an acute exacerbation of chronic HBV infection in a patient with underlying cirrhosis. ### Serological Interpretation | Marker | Result | Interpretation | |--------|--------|----------------| | HBsAg | Positive | Indicates chronic HBV infection | | Anti-HBc | Positive | Confirms past/present HBV exposure | | Anti-HBs | Negative | No immunity; active infection | | Anti-HAV IgM | Negative | Rules out acute hepatitis A | | HCV antibody | Negative | Rules out HCV co-infection | | HBV DNA | 8.5 × 10^6 copies/mL | High viral load; active replication | **High-Yield:** **HBsAg positivity for >6 months** (implied by the 15-year alcohol history and chronic liver disease features) defines chronic hepatitis B. The acute presentation with fever and RUQ pain superimposed on cirrhosis is the **acute-on-chronic** flare. ### Evidence of Decompensated Cirrhosis 1. **Clinical signs:** Ascites, spider angiomas → portal hypertension and hepatic decompensation 2. **Synthetic dysfunction:** INR 1.8 (>1.5), albumin 2.9 g/dL (<3.5) → impaired hepatic protein synthesis 3. **Thrombocytopenia:** 85,000/μL → bone marrow suppression from portal hypertension and splenomegaly 4. **Cholestasis:** Elevated ALP (240 IU/L) with mild transaminitis (AST 320, ALT 180) → pattern consistent with cirrhosis, not acute viral hepatitis alone **Clinical Pearl:** In acute-on-chronic hepatitis B, transaminases are often only **mildly to moderately elevated** (AST/ALT <1000 IU/L) because the underlying cirrhosis has already destroyed much of the hepatic parenchyma. In contrast, acute hepatitis B alone typically shows **marked transaminitis** (AST/ALT >1000 IU/L). ### Pathophysiology of Acute-on-Chronic Flare ```mermaid flowchart TD A[Chronic HBV infection]:::outcome --> B[Cirrhosis develops over years] B --> C[Acute viral reactivation or superinfection]:::action C --> D[Massive hepatocyte necrosis] D --> E{Hepatic reserve?}:::decision E -->|Adequate| F[Acute hepatitis, self-limited]:::outcome E -->|Exhausted| G[Acute-on-chronic decompensation]:::urgent G --> H[Ascites, coagulopathy, encephalopathy]:::urgent ``` ### Why Alcohol Use Disorder Is a Cofactor, Not the Primary Diagnosis - Alcohol accelerates HBV-related cirrhosis and increases risk of HBV reactivation - However, **HBsAg positivity and high HBV DNA** are the drivers of the acute illness - Alcoholic hepatitis alone would show **AST > ALT** (ratio >2) and **elevated GGT**; here ALT is relatively preserved and the serological profile is clearly HBV-driven **Mnemonic:** **AOCH-B** = **A**cute **O**n **C**hronic **H**epatitis **B**: Pre-existing cirrhosis + acute viral flare = decompensation.