Autoimmune hepatitis in children: what is different from adult AIH?

Autoimmune hepatitis (AIH) is characterized by inflammatory liver histology, circulating non-organ-specific autoantibodies, and increased levels of immunoglobulin (Ig) G in the absence of a known etiology. Two types of childhood AIH are recognized according to seropositivity: smooth muscle antibody (SMA) and/or antinuclear antibody (ANA), which is AIH type 1; and antibodies to liver-kidney microsome type 1 (anti-LKM1), which is AIH type 2. There is a female predominance in both. Autoimmune hepatitis type 2 presents more acutely, at a younger age, and commonly with IgA deficiency; however, duration of symptoms before diagnosis, clinical signs, family history of autoimmunity, presence of associated autoimmune disorders, response to treatment, and long-term prognosis are similar in the two groups. Immunosuppressive treatment with steroids and azathioprine, which should be instituted promptly to avoid progression to cirrhosis, induces remission in 80% of cases. Relapses are common, often due to nonadherence. Drugs effective in refractory cases include cyclosporine and mycophenolate mofetil. Long-term treatment is usually required, with only some 20% of AIH type 1 patients able to discontinue therapy successfully. In childhood, sclerosing cholangitis with strong autoimmune features, including interface hepatitis and serological features identical to AIH type 1, is as prevalent as AIH, but it affects boys and girls equally. The differential diagnosis relies on cholangiographic studies. In autoimmune sclerosing cholangitis, liver parenchymal damage responds satisfactorily to immunosuppressive treatment, whereas bile duct disease tends to progress.