Severe HBV-Associated Hepatitis in Infants from the Same Family: Two Clinical Cases with Different Outcomes.

Acute hepatitis B virus (HBV) infection is rare during infancy, and severe symptomatic HBV-associated hepatitis is even less common. We describe two siblings who developed severe HBV-associated liver injury during infancy, two years apart, but experienced markedly divergent clinical outcomes. Clinical, laboratory, virological, microbiological, imaging, therapeutic, and follow-up data were retrospectively reviewed. Household members were subsequently tested for HBV and HDV. The first infant, a 5-month-old girl, presented with HBsAg positivity, negative serological markers for HAV, HCV, and HEV, and severe acute liver injury with a fulminant clinical course that resulted in death. Because anti-HBc IgM, HBV DNA, repeat HBsAg testing, and follow-up serology were unavailable, acute HBV infection could not be confirmed, and the episode was therefore classified as presumed HBV-associated fulminant hepatitis. The rapidly fatal clinical course precluded a comprehensive etiological evaluation, and the available medical records did not fully document the diagnostic work-up. The second patient, a 4-month-old boy, presented with serological and molecular evidence of acute HBV infection, including low-level HBV DNA, total anti-HDV positivity of uncertain clinical significance, and positive CMV IgM/IgG serology. He also had a urinary tract infection (UTI) caused by extended-spectrum β-lactamase (ESBL)-producing