Hepatitis D Virus (HDV) in Pediatrics

Introduction

Hepatitis D virus (HDV), also called hepatitis delta virus, is a unique, defective, single‐stranded RNA virus that requires the hepatitis B surface antigen (HBsAg) for assembly and transmission. Although HDV is less common than other hepatitis viruses, coinfection or superinfection with HDV accelerates the course of hepatitis B virus (HBV)–associated liver disease, increasing the risk of cirrhosis, hepatic decompensation, and hepatocellular carcinoma in children.

Virology and Genotypes

HDV is the smallest human virus, encoding a single protein—the delta antigen—within a circular RNA genome. Its replication occurs via host RNA polymerase II in the nucleus of infected hepatocytes, independent of HBV replication. Eight HDV genotypes (I–VIII) have been identified, with genotype I predominating globally and in the United States. Genotypic variation influences disease severity and response to therapy.

Transmission

HDV is spread by the same routes as HBV:

• Vertical transmission: Mother to infant at birth; risk mirrors that of HBV.
• Parenteral/percutaneous exposure: Needle sticks, blood transfusion, or unsafe medical procedures.
• Sexual transmission: Occasional in adolescents and adults.

Clinical Manifestations

Acute HDV infection presents with nonspecific prodromal symptoms—fatigue, lethargy, anorexia, nausea—followed by jaundice, right upper quadrant discomfort, and elevated aminotransferases. The course differs depending on the context of HBV infection.

Acute Infection: Coinfection vs. Superinfection

Acute hepatitis D occurs in two patterns:

• Coinfection: Simultaneous acute infection with HBV and HDV. Clinical severity is similar to acute HBV alone, with a low risk (<5%) of fulminant hepatic failure in children.
• Superinfection: HDV infection of a child chronically infected with HBV. This often triggers a severe hepatitis flare, with a high risk of progression to chronic HDV infection (>80%) and rapid development of cirrhosis.

Chronic Infection and Long-Term Outcomes

HDV superinfection frequently leads to chronic HDV, which carries a more aggressive course than HBV monoinfection. Children with chronic HDV are at greater risk for cirrhosis, hepatic decompensation, and hepatocellular carcinoma at earlier ages.

Diagnosis

Diagnostic evaluation in HBsAg-positive children includes:

• Anti-HDV IgM and IgG: Detects recent or past exposure to HDV.
• HDV RNA PCR: Confirms active replication and quantifies viral load.
• Assessment of liver function tests and imaging to stage disease severity.

Treatment

There is no HDV-specific antiviral approved for children; management is challenging and often extrapolated from adult data.

Supportive Care

• Monitor liver function and signs of hepatic decompensation.
• Manage complications such as ascites, encephalopathy, or coagulopathy.

Pegylated Interferon-α

Long-acting interferon-α remains the only therapy with demonstrated efficacy against HDV in children. A 48-week course yields sustained virologic response rates of 20–30 percent. Treatment should be considered in children with compensated liver disease and evidence of active HDV replication.

Novel Therapies Under Investigation

• Bulevirtide (Myrcludex B): An HBV/HDV entry inhibitor approved for adults; emerging pediatric data suggest safety and efficacy in reducing HDV RNA levels and improving liver inflammation.
• Lonafarnib: A prenylation inhibitor that disrupts HDV assembly; combination with ritonavir and/or PEG-IFN shows promise in early trials.
• HBV-directed nucleos(t)ide analogues: Though they suppress HBV, they have limited direct impact on HDV but may be used concomitantly to control HBV replication.

Liver Transplantation

Children with end-stage liver disease or fulminant hepatic failure may require transplantation. Posttransplant recurrence of HDV is nearly universal without effective antiviral prophylaxis; combining interferon or novel agents with HBV immunoprophylaxis and antivirals is recommended.

Prevention

Prevention of HDV hinges on HBV immunization and standard infection control:

• HBV vaccination: Universal immunization of infants and susceptible children prevents HDV infection by eliminating the helper HBV surface antigen required for HDV assembly.
• Standard precautions: Avoid sharing needles, razors, toothbrushes, or nail clippers; use universal blood-borne pathogen precautions in healthcare and home settings.

Hepatitis D in Pregnancy and Neonatal Guidance

HDV risk in pregnancy mirrors that of HBV. There is no specific maternal prophylaxis for HDV; prevention relies on:

• Screening HBsAg-positive pregnant women and administering HBV immune globulin and HBV vaccine to newborns within 12 hours of birth.
• Deferring HDV-specific therapy until postpartum; emerging safety data on bulevirtide and lonafarnib in pregnancy are limited.
• Encouraging breastfeeding unless maternal nipples are bleeding or coinfection with HIV is present.

Conclusion

Hepatitis D complicates the course of HBV infection in children, accelerating progression to cirrhosis and HCC. Early recognition of coinfection or superinfection, judicious use of pegylated interferon-α, and emerging therapies such as bulevirtide and prenylation inhibitors offer hope for improved outcomes. Universal HBV vaccination remains the cornerstone of HDV prevention, underscoring the vital role of pediatric immunization programs.