Pathology of autoimmune liver diseases in children

Liver disorders are more diverse in children than in adults, and autoimmune liver diseases also develop in childhood, although rarely. The autoimmune diseases in children comprise autoimmune hepatitis (AIH) and primary sclerosing cholangitis (PSC). The pathology of AIH and PSC is described. Although AIH in children is rare, it occurs in early childhood, and some elementary school students have been reported to develop cirrhosis. The histology of AIH in children is essentially the same as that in adults. We analyzed eight patients with childhood AIH. Four of these patients had a high AIH score, with typical histological features of AIH, that is, interface hepatitis with infiltration of lymphocytes and plasma cells, a severe necroinflammatory reaction and rosette formation of hepatocytes. Multinucleated hepatocytes were observed in three patients. This finding seems characteristic of childhood AIH, although rarely observed in adult AIH. Clinically, the distinction between AIH and PSC is often difficult in childhood, and the overlapping of both has also been reported. PSC-like histological features may be observed in some pediatric patients with AIH. In patients with acute onset of AIH, they show a pronounced necroinflammatory reaction in zone 3 (central area). Because an autoimmune phenomenon may occur in the early stage of childhood PSC, it is difficult to differentiate it from AIH in some patients. Some patients are diagnosed with AIH in the early stage, but with PSC during long-term follow up. The histopathological findings of childhood PSC are the same as those of adult PSC, and are characterized by biliary-type portal fibrosis and onion-like periductal fibrosis in medium-sized portal tracts.