A 42-year-old woman from Mumbai with a 12-year history of hepatitis B (HBsAg positive, anti-HBe positive) on no antiviral therapy presents with acute-onset jaundice, fever (38.5°C), right upper quadrant pain, and malaise for 5 days. She denies recent drug use or transfusion. Laboratory findings: total bilirubin 9.8 mg/dL, ALT 3200 IU/L, AST 2800 IU/L, ALP 220 IU/L, albumin 3.2 g/dL, INR 1.4. HBsAg remains positive; anti-HBc IgM is negative; HBV DNA is 8.5 × 10^6 copies/mL (previously 1.2 × 10^4 copies/mL 6 months ago). What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Hepatitis B Flare (Spontaneous Reactivation) ### Key Diagnostic Features **Key Point:** The diagnosis of HBV flare is established by: - **Chronic HBsAg positivity** (12-year history) with anti-HBc IgM **negative** (rules out acute HBV) - **Sudden ≥100-fold increase in HBV DNA** (from 1.2 × 10^4 to 8.5 × 10^6 copies/mL) - Acute clinical presentation (fever, jaundice, RUQ pain) superimposed on chronic infection - Marked transaminitis (ALT 3200 IU/L) with mild synthetic dysfunction (INR 1.4, albumin 3.2 g/dL) ### Pathophysiology of HBV Flare ```mermaid flowchart TD A[Chronic HBV infection]:::outcome --> B{Immune trigger?}:::decision B -->|Spontaneous reactivation| C[Loss of immune tolerance]:::action B -->|Superinfection| D[Coinfection with HAV/HDV]:::action C --> E[Rapid HBV replication]:::action D --> F[Rapid HBV replication]:::action E --> G[Acute hepatitis flare]:::outcome F --> G G --> H{Outcome?}:::decision H -->|Fulminant| I[Liver transplant]:::urgent H -->|Non-fulminant| J[Recovery with treatment]:::action ``` ### Serological Interpretation | Marker | Finding | Interpretation | |--------|---------|----------------| | HBsAg | Positive | Chronic HBV | | Anti-HBc IgM | **Negative** | Rules out acute HBV; confirms chronic infection | | Anti-HBe | Positive | HBeAg-negative phase | | HBV DNA | 8.5 × 10^6 copies/mL | Massive increase (>100-fold) | | HBV DNA trend | 1.2 × 10^4 → 8.5 × 10^6 | Spontaneous reactivation | **High-Yield:** Anti-HBc IgM negativity is the critical discriminator between acute HBV (IgM positive) and HBV flare in chronic infection (IgM negative). ### Clinical Context: Why Flare, Not Superinfection? **Clinical Pearl:** - **Hepatitis A superinfection:** Would require positive anti-HAV IgM (not mentioned; likely tested and negative) - **Hepatitis C superinfection:** Would require anti-HCV or HCV RNA positivity (not mentioned) - **Hepatitis D superinfection:** Would require anti-HDV or HDV RNA (not mentioned) - **Spontaneous HBV reactivation:** Occurs in 20–30% of chronic HBsAg carriers, especially those with high baseline HBV DNA or immune dysfunction The absence of serological evidence for HAV, HCV, or HDV, combined with the massive HBV DNA surge in a known chronic carrier, points to spontaneous HBV reactivation. ### Management **Key Point:** - Initiate nucleos(t)ide reverse transcriptase inhibitor (e.g., tenofovir or entecavir) - Monitor INR and bilirubin closely; assess for fulminant hepatic failure - Supportive care and avoid hepatotoxic agents - Prognosis depends on degree of synthetic dysfunction; INR 1.4 suggests compensated flare [cite:Harrison 21e Ch 297]