Hepatitis D
Virology And Pathogenesis
- Defective, single-stranded circular RNA virus.
- Smallest known animal virus (36-nm diameter).
- Requires concurrent hepatitis B virus (HBV) infection for replication and infection.
- Outer viral coat composed of excess hepatitis B surface antigen (HBsAg).
- Inner core expresses specific hepatitis D virus (HDV) antigen.
- Induces direct cytopathic injury to hepatocytes.
- Associated with severe liver damage.
Clinical Manifestations
- Transmitted parenterally or via intrafamilial/intimate contact.
- Presents exclusively in association with HBV infection.
Infection Modalities
| Modality | Acquisition Timing | Clinical Features | Prognosis |
|---|---|---|---|
| Coinfection | Simultaneous acquisition of HBV and HDV. | Severe acute hepatitis. Incubation 21-42 days. | Low risk of developing chronic hepatitis. |
| Superinfection | HDV acquisition in established chronic HBV carrier. | Acute illness rare. Accelerates and worsens underlying HBV course. | High risk of chronic hepatitis. Highest risk of acute liver failure. |
Diagnostic Evaluation
- Commercial assays detect IgM and IgG antibodies.
- Polymerase chain reaction (PCR) detects viral RNA (primarily research utility).
| Disease State | Diagnostic Markers |
|---|---|
| Acute Infection | Anti-HDV IgM positive. Develops 2-4 weeks after coinfection, 10 weeks after superinfection. |
| Chronic Infection | Anti-HDV IgG positive, blood PCR positive, HBsAg positive. |
| Resolved Infection | Anti-HDV IgG positive, blood PCR negative. |
Management And Prevention
- Specific HDV-targeted pharmacotherapy unavailable.
- Medical therapy relies on supportive care.
- Pegylated interferon utilized as primary antiviral agent.
- Specific HDV vaccine nonexistent.
- Prevention relies entirely on preventing primary HBV infection via hepatitis B vaccination and hepatitis B immunoglobulin (HBIG).