Biliary epithelial changes in pediatric autoimmune hepatitis with normal cholangiography: diagnostic caution for autoimmune sclerosing cholangitis overlap.

A 7.5-year-old boy with one month of persistent jaundice was found to have elevated transaminases, hypergammaglobulinemia, negative viral hepatitis markers, normal ceruloplasmin and 24-hour urinary copper levels. Antinuclear antibody and p-ANCA were positive. Magnetic resonance cholangiography showed normal intra and extrahepatic bile ducts, and inflammatory bowel disease screening was negative. Liver biopsy revealed interface hepatitis with portal lymphoplasmacytic infiltrates and bridging fibrosis. Interlobular bile ducts showed mucinous metaplasia, consistent with chronic bile duct injury. The diagnosis of AIH was made, and he was started on corticosteroids and azathioprine, following which he showed sustained normalization of transaminases at four-month follow-up. AIH and ASC lie on a diagnostic spectrum in children and, distinguishing small-duct ASC from AIH can be difficult. The presence of biliary epithelial injury in the setting of serological p-ANCA positivity in a child with AIH raises suspicion of AIH-ASC overlap. Mucinous metaplasia may reflect chronic biliary epithelial injury, but in isolation it is not diagnostic of ASC. In children with AIH, such findings should prompt careful biochemical and radiological follow-up especially when cholangiography is initially normal. This report emphasizes the diagnostic challenge encountered at the intersection of AIH and ASC in children. It reinforces that, although biliary involvement may suggest overlap disease, a primary diagnosis of AIH should be considered when cholangiographic and clinical progression are absent, and that continued surveillance is warranted to guide long-term management.