A 28-year-old woman from Mumbai is evaluated for abnormal liver function tests found on routine screening. She is asymptomatic and denies jaundice, dark urine, or abdominal pain. Her liver enzymes are mildly elevated (ALT 120 IU/L, AST 95 IU/L). Serological testing reveals: HBsAg positive, anti-HBc IgM negative, anti-HBc IgG positive, HBeAg negative, anti-HBe positive, anti-HBs negative. HBV DNA is detectable at 2 × 10^4 copies/mL. What is the most likely diagnosis?

Explanation

## Diagnosis: Chronic Hepatitis B — HBeAg-Negative Phase ### Key Serological Pattern Recognition **Key Point:** HBsAg persistence >6 months + anti-HBc IgM negative + anti-HBc IgG positive = chronic infection. The absence of HBeAg with presence of anti-HBe indicates the low-replication (HBeAg-negative) phase. ### Serological Differentiation: Acute vs. Chronic | Feature | Acute HBV | Chronic HBV | |---------|-----------|-------------| | **Anti-HBc IgM** | Positive | Negative | | **Anti-HBc IgG** | Negative initially, then positive | Positive | | **HBsAg Duration** | Clears within 6 months | Persists >6 months | | **Clinical Presentation** | Symptomatic (jaundice, malaise) | Often asymptomatic | | **ALT Elevation** | Marked (>1000 IU/L) | Mild to moderate | **High-Yield:** Anti-HBc IgM negative is the single best marker to exclude acute HBV and confirm chronic infection. ### HBeAg Status and Replication Phases ```mermaid flowchart TD A["Chronic HBV<br/>(HBsAg+, anti-HBc IgG+)"]:::outcome --> B{"HBeAg Status?"}:::decision B -->|"HBeAg+<br/>Anti-HBe−"|C["HBeAg-Positive Phase<br/>(High replication)<br/>HBV DNA usually >10^5 copies/mL"]:::outcome B -->|"HBeAg−<br/>Anti-HBe+"|D["HBeAg-Negative Phase<br/>(Low replication)<br/>HBV DNA <10^5 copies/mL<br/>but often detectable"]:::outcome C --> E["Higher infectivity<br/>Rapid progression risk"]:::urgent D --> F["Lower infectivity<br/>But still infectious<br/>Can have flares"]:::action ``` ### Why This Is HBeAg-Negative Phase 1. **HBeAg negative, anti-HBe positive** — Indicates seroconversion from HBeAg to anti-HBe, characteristic of the low-replication phase. 2. **HBV DNA detectable but modest** (2 × 10^4 copies/mL) — In HBeAg-negative phase, HBV DNA is typically <10^5 copies/mL but remains detectable. HBeAg-positive phase usually has HBV DNA >10^5 copies/mL. 3. **Mildly elevated transaminases** — Consistent with chronic HBV with low replication. Acute HBV would show marked elevation (>1000 IU/L). 4. **Asymptomatic presentation** — Typical of chronic HBV, especially in the low-replication phase. Acute HBV usually presents with jaundice and systemic symptoms. **Clinical Pearl:** HBeAg-negative chronic HBV can still progress to cirrhosis and HCC, especially if HBV DNA remains detectable. These patients require monitoring even without HBeAg positivity. ### Why Not HBeAg-Positive Phase? HBeAg-positive phase would show HBeAg positive and anti-HBe negative. This patient has the opposite (HBeAg negative, anti-HBe positive), indicating seroconversion to the low-replication phase. ### Why Not Acute Infection? Anti-HBc IgM is negative, which rules out acute HBV. Acute infection requires anti-HBc IgM positivity. Additionally, the clinical presentation (asymptomatic, mild transaminitis) is inconsistent with acute hepatitis B. ### Why Not Occult Replication? Occult HBV is defined as HBsAg negativity with detectable HBV DNA. This patient is HBsAg positive, so the infection is overt, not occult.