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Autoimmune hepatitis (AIH) is characterised by female predominance, interface hepatitis, hypergammaglobulinaemia, and autoantibodies.1 ,2 Typically, the disease responds well to corticosteroid therapy, and clinical, laboratory, and histological remission can be achieved in 65% of patients within 18 months.3 ,4 Among Caucasoid Northern Europeans, its mean annual incidence is 1.9 per 100 000, and its point prevalence is 16.9 per 100 000.5 In the USA, AIH affects 100 000–200 000 individuals.6 It accounts for 2.6% of the liver transplants in the European Liver Transplant Registry7 and 5.9% of liver transplants in the USA.8
Classical autoimmune hepatitis
Three types of AIH have been proposed based on immunoserological findings but only two types have mutually exclusive autoantibodies and different clinical profiles.9 Type 1 AIH is the most common form of the disease worldwide and is associated with antinuclear antibodies (ANA) and/or smooth muscle antibodies (SMA). It affects all age groups and is associated with human leucocyte antigen (HLA) DR3 (DRB1*0301) and DR4 (DRB1*0401) in Caucasoid Northern European and North American patients.10 ,11 DRB1*0301 andDRB1*0401 influence disease expression and behaviour as well as susceptibility. Caucasoid patients with type 1 AIH and DRB1*0301 are younger, and have a higher frequency of treatment failure,12 relapse after drug withdrawal,13 and requirement for liver transplantation than patients with other alleles.14 In contrast, patients with DRB1*0401 are typically older, frequently have concurrent autoimmune diseases, and respond better to corticosteroids than counterparts withDRB1*0301.15
Type 2 AIH affects mainly children and is characterised by antibodies to liver/kidney microsome type 1 (anti-LKM1).16 The target autoantigen of type 2 AIH is the cytochrome mono-oxygenase P450 IID6 (CYP2D6),17 ,18 and five antigenic sites located between peptides 193–212, 257–269, 321–351, 373–389, and 410–429 are recognised by anti-LKM1. …