Natural history of chronic hepatitis B virus infection in children in Japan: a comparison of mother-to-child transmission with horizontal transmission.

Background: It is necessary to evaluate the natural history of children with hepatitis B virus (HBV) infection in each country to consider their long-term management.
Methods: A multi-center observational study of children with chronic HBV infection who were diagnosed at age ≤15 years was carried out in 18 hospitals in Japan.
Results: We reviewed children with HBV infection including 381 with mother-to-child transmission (MTCT) and 154 with horizontal transmission, genotype C being the most prevalent virus genotype (83%). Children with horizontal transmission were more frequently infected with HBV genotype A or B and more likely to receive interferon therapy than those infected by MTCT. The HBeAg seroconversion rate at 15 years of age was 42% in the MTCT group and 38% in the horizontal group. It was lower in children with genotype C infection than in those infected with other genotypes (33 versus 45%). Hepatitis developed at any age but before 4 years of age the incidence was high in the horizontal group. At 3 years after the onset of the hepatitis, 26% of children with MTCT and 30% of those with horizontal transmission became inactive carriers. The incidences of hepatocellular carcinoma (HCC) at 30 years of age were 6% in the MTCT group and 11% in the horizontal group.
Conclusions: Patients with childhood-onset HBV infection with MTCT and horizontal transmission developed hepatitis and seroconverted to anti-HBe at any age and had a lifetime risk of developing HCC.