1238 Autoimmune Hepatitis Mayo Clin Proc, December 2001, Vol 76 Table 1. Criteria for the Diagnosis of Autoimmune Hepatitis* Diagnostic criteria Diagn

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1 Mayo Clin Proc, December 2001, Vol 76 Autoimmune Hepatitis 1237 Review Current Concepts in the Diagnosis, Pathogenesis, and Treatment of Autoimmune Hepatitis JAMEELA ABDULLAH AL-KHALIDI, MD, AND ALBERT J. CZAJA, MD Autoimmune hepatitis has a global distribution and affects all ages. Genetic factors strongly influence susceptibility, clinical expression, and treatment response. The diagnosis of autoimmune hepatitis has been codified by an international panel. An acute or fulminant presentation is recognized but not a cholestatic form. Subclassifications by predominant autoantibody profile have been proposed, but they lack etiologic and prognostic differences. Autoantibodies continue to be characterized to improve diagnostic specificity, predict outcome, and identify pertinent antigenic targets. Cytosolic enzymes are prime candidates as autoantigens. DRB1*0301 and DRB1*0401 are the susceptibility alleles in Caucasoid Northern Europeans and North Americans, and they also affect clinical expression and treatment outcome. Other autoimmune promoters affecting cytokine production and immunocyte activation may act in synergy with the susceptibility alleles to affect disease behavior. Cell-mediated and antibody-dependent Autoimmune hepatitis is unresolving inflammation of the liver of unknown cause associated with interface hepatitis on histological examination, hypergammaglobulinemia, and autoantibodies. 1-5 An international panel has codified the diagnostic criteria, and the definite diagnosis requires exclusion of hereditary (Wilson disease, genetic hemochromatosis, and α 1 -antitrypsin deficiency), viral (hepatitis A, B, and C virus infection), and drug-induced (minocycline, isoniazid, α-methyldopa hydrazine, and nitrofurantoin) conditions (Table 1). 6,7 Autoimmune hepatitis is not a viral disease, and it is not associated with epidemiological risk factors for viral infection (blood transfusions, needlesticks, tattoos, and intravenous drug use), alcohol injury (>60 g/d), or drug toxicity. 6,7 The manifestations of autoimmunity must be substantial with high-titer autoantibodies and pronounced hypergammaglobulinemia, and no clinical, laboratory, or histological manifestations of cholestasis can be present. A cholestatic form of autoimmune hepatitis is not recognized (Table 1). 6,7 forms of cytotoxicity are probably interactive pathogenic mechanisms, and novel site-specific therapies are feasible because these mechanisms are defined. Potent new immunosuppressive agents are emerging from the transplantation arena, but prednisone alone or in combination with azathioprine remains the mainstay of treatment. Corticosteroid therapy is effective but not ideal. Mayo Clin Proc. 2001;76: anti-lc1 = antibodies to liver cystosol type 1; anti-lkm1 = antibodies to liver-kidney microsome type 1; anti-sla/lp = antibodies to soluble liver antigen/liver pancreas; APS1 = autoimmune polyglandular syndrome type 1; anti-asgpr = antibodies to asialoglycoprotein receptor; AST = aspartate aminotransferase; CTLA-4 = cytotoxic T-lymphocyte antigen 4 gene; ELISA = enzyme-linked immunosorbent assay; IL = interleukin; MHC = major histocompatibility complex; panca = perinuclear antineutrophil cytoplasmic antibodies; SMA = smooth muscle antibodies The diagnosis of autoimmune hepatitis can be confirmed by applying a scoring system that grades individual components of the syndrome (Table 2). 6-8 The composite score counterbalances typical features of the disease against inconsistent or weak findings and reflects the likelihood of a correct diagnosis. Furthermore, a pretreatment diagnosis can be revised after assessment of treatment outcome. Responsiveness to corticosteroid therapy upgrades the composite score and supports a definite diagnosis of autoimmune hepatitis. The scoring system provides an objective means by which to assess the strength of the diagnosis, evaluate variant syndromes, and compare populations in different geographical regions and treatment trials It was revised by the International Autoimmune Hepatitis Group in 1999 for a more accurate exclusion of the cholestatic syndromes. 7 Preliminary experiences have supported its ability in this regard, but the revised system has not yet been validated prospectively. Often, the scoring system is unnecessary for a confident diagnosis. From the Department of Gastroenterology, Al Amiri Hospital, Kuwait (J.A.A.-K.); and Division of Gastroenterology and Hepatology and Internal Medicine, Mayo Clinic, Rochester, Minn (A.J.C.). Address reprint requests and correspondence to Albert J. Czaja, MD, Division of Gastroenterology and Hepatology, Mayo Clinic, 200 First St SW, Rochester, MN ( czaja.albert@mayo.edu). FREQUENCY AND ETHNIC DISTRIBUTION Autoimmune hepatitis afflicts 100,000 to 200,000 persons in the United States 12 and accounts for 2.6% of transplant recipients in Europe 13 and 5.9% in the United States. 14 Among Caucasoid Northern Europeans, the mean annual Mayo Clin Proc. 2001;76: Mayo Foundation for Medical Education and Research

2 1238 Autoimmune Hepatitis Mayo Clin Proc, December 2001, Vol 76 Table 1. Criteria for the Diagnosis of Autoimmune Hepatitis* Diagnostic criteria Diagnostic requisites Definite AIH Probable AIH Exclude hereditary Normal α 1 -AT phenotype, normal Partial α 1 -AT deficiency, abnormal diseases ceruloplasmin level, normal iron copper or ceruloplasmin level but and ferritin levels Wilson disease excluded, nonspecific iron and/or ferritin abnormalities Exclude viral diseases No active hepatitis A, B, and/or No active hepatitis A, B, and/or C infection C infection Exclude alcohol- or Daily alcohol intake <25 g/d, no Daily alcohol intake <50 g/d, no drug-related disease recent hepatotoxic drugs recent hepatotoxic drugs Demonstrate hepatitic Predominant serum Predominant serum features aminotransferase abnormality aminotransferase abnormality Document immune Globulin, γ-globulin, or serum IgG Hypergammaglobulinemia of any reactivity level 1.5 times normal; ANA, SMA, degree; ANA, SMA, or anti-lkm1 or anti-lkm1 1:80 in adults and 1:40 in adults; other autoantibodies 1:20 in children; no AMA Describe compatible Interface hepatitis, moderate to severe; Interface hepatitis, moderate to severe; histological features no biliary lesions, granulomas, or no biliary lesions, granulomas, or prominent changes suggestive of prominent changes suggestive of another disease another disease *AIH = autoimmune hepatitis; AMA = antimitochondrial antibodies; ANA = antinuclear antibodies; anti- LKM1 = antibodies to liver-kidney microsome type 1; α 1 -AT = α 1 -antitrypsin; SMA = smooth muscle antibodies. incidence of autoimmune hepatitis is 1.9 per 100,000 population, and its point prevalence is 16.9 per 100,000 population. 15 Autoimmune hepatitis occurs predominantly in women and affects all ages. Originally described in Caucasoid Northern Europeans and North Americans, autoimmune hepatitis has been recognized in black, 16 Hispanic, 17 Arab, 18 and Japanese 19 populations, and it has a worldwide distribution. SUBCLASSIFICATIONS Three types of autoimmune hepatitis have been proposed based on immunoserologic markers (Table 3). 20 The International Autoimmune Hepatitis Group has not endorsed these types as distinct clinical or etiologic entities. 6,7 Nevertheless, they are useful designations and have been incorporated into the clinical jargon. Type 1 and type 2 autoimmune hepatitis have different clinical features, whereas type 3 autoimmune hepatitis is similar to type 1 except for its autoantibody profile. As etiologic, genetic, and/or pathogenic distinctions are defined, the classification scheme may change. Type 1 Type 1 autoimmune hepatitis is characterized by the presence of antinuclear antibodies and/or smooth muscle antibodies (SMA) (Table 3). 20 It is the most common form of the disease worldwide, especially in Caucasoid Northern Europeans and North Americans. Of patients with type 1 autoimmune hepatitis, 70% are women younger than 40 years, and more than 30% have concurrent immune diseases, especially autoimmune thyroiditis, synovitis, or ulcerative colitis. 1 Onset of symptoms is abrupt in 40% of patients, and rarely the disease may have a fulminant presentation. 21 The 6-month requirement to establish chronicity has been waived, and the diagnosis of autoimmune hepatitis can be made at initial presentation. 6,7 The propensity for an abrupt onset must be recognized so that a misdiagnosis of acute viral or toxic hepatitis can be avoided, and appropriate, potentially life-saving corticosteroid therapy can be instituted promptly At presentation, 25% of patients have cirrhosis, indicating that type 1 autoimmune hepatitis has an indolent, aggressive subclinical stage The target autoantigen of type 1 autoimmune hepatitis is unknown. The asialoglycoprotein receptor is a candidate autoantigen because it resides on the hepatocyte surface, captures and transports peptides, and generates antibodies commonly present in autoimmune hepatitis Cytosolic enzymes have been incriminated in other forms of auto immune hepatitis and must be studied in type 1 disease. Cytochrome monooxygenases, such as P-450 IID6 (CYP2D6), 31,32 P-450 IA2, and P-450 IA6, 33,34 and other enzymes, such as uridine diphosphate glucuronosyltransferase, 35,36 glutathione S-transferases, 37 formiminotransferase cyclodeaminase, 38 argininosuccinate lyase, 39 and E2 subunits of pyruvate dehydrogenase complex, 40,41 are examples of enzyme targets already implicated in autoimmune liver disease.

3 Mayo Clin Proc, December 2001, Vol 76 Autoimmune Hepatitis 1239 Antinuclear antibodies and SMA are not disease specific or pathogenic. 42 However, their full characterization remains important because each may be an imprint of a pathogenic mechanism and a clue to a pertinent autoantigen. Antinuclear antibodies react against multiple nuclear antigens, including histones, ribonucleoproteins, ribonucleoprotein complexes, and centromere, and the patterns of nuclear immunofluorescence do not characterize clinical subgroups. 46 Patients with a speckled pattern of antinuclear antibody reactivity are younger and have higher serum levels of aspartate aminotransferase (AST) than do patients with a homogeneous pattern. However, these group distinctions are not discriminative in individual patients. Assays based on indirect immunofluorescence have been replaced in many clinical laboratories by enzyme-linked immunosorbent assays (ELISAs) based on recombinant nuclear antigens. 47,48 The comparability of these different assay systems in the evaluation of autoimmune hepatitis remains unproved. Smooth muscle antibodies exhibit reactivities against actin and nonactin components (tubulin, vimentin, desmin, and skeletin), and individual reactivities have not been widely accepted as having diagnostic and prognostic value. 48,51 Antibodies to actin (antiactin) identify a subgroup of patients with SMA who have disease at an earlier age and a poorer response to corticosteroid therapy. 52 However, the assay for antiactin has not been established, and its incorporation into conventional diagnostic strategies has been limited. 53,54 Other autoantibodies of potential diagnostic and/or prognostic value in type 1 autoimmune hepatitis are perinuclear antineutrophil cytoplasmic antibodies (pancas) 55,56 and antibodies to asialoglycoprotein receptor (anti-asgpr) Perinuclear antineutrophil cytoplasmic antibodies occur in 50% to 90% of patients with type 1 autoimmune hepatitis 55,56 but are absent in patients with type 2 disease. 56 They are mainly of the IgG1 isotype, which distinguishes them from the pancas in primary sclerosing cholangitis. 55 Typically, these antibodies are present in high titer in type 1 autoimmune hepatitis and have not had prognostic importance. Actin has been proposed as the target antigen, 57 but recent studies have suggested reactivity against granulocyte-specific antigens in the nuclear lamina. 58 As such, pancas may be better designated as antineutrophil nuclear antibodies. Their major clinical value in type 1 autoimmune hepatitis may be to reclassify patients with cryptogenic chronic hepatitis as having autoimmune hepatitis. 59 A generic marker for autoimmune hepatitis, anti- ASGPR are present in all forms of the disease. 30 Seropositivity is associated with laboratory and histological indices of disease activity, and anti-asgpr identify patients who Table 2. Scoring Criteria for the Diagnosis of Autoimmune Hepatitis* Factors Score Female sex +2 Alk phos-ast (ALT) ratio >3 2 < γ-globulin or serum IgG levels (nl) > ANA, SMA, or anti-lkm1 >1: : :40 +1 <1:40 0 Antimitochondrial antibodies 4 Viral markers Seropositive 3 Seronegative +3 Hepatotoxic drugs Yes 4 No +1 Alcohol use <25 g/d +2 >60 g/d 2 HLA-DR3 or HLA-DR4 +1 Concurrent immune disease +2 Other liver-related autoantibody +2 Interface hepatitis +3 Plasmacytic infiltrate +1 Rosettes +1 No characteristic features 5 Biliary changes 3 Other features (fat, granulomas) 3 Treatment response complete +2 Relapse +3 *Pretreatment score: definite diagnosis, >15; probable diagnosis, Posttreatment score: definite diagnosis, >17; probable diagnosis, Alk phos-ast = ratio of serum alkaline phosphatase to aspartate aminotransferase level; ALT = serum alanine aminotransferase level. The remaining abbreviations are explained in the footnote to Table 1. commonly will have a relapse after corticosteroid withdrawal. 60,61 The development of a commercial assay for application of anti-asgpr has been difficult, and their potential as diagnostic and prognostic markers has not yet been realized. Type 2 Type 2 autoimmune hepatitis is characterized by the presence of antibodies to liver-kidney microsome type 1 (anti-lkm1) (Table 3). 62 These antibodies react against the proximal tubules of the murine kidney and the cytoplasm of the murine liver. 48,51 These patterns of indirect immunofluorescence distinguish anti-lkm1 from antimitochon-

4 1240 Autoimmune Hepatitis Mayo Clin Proc, December 2001, Vol 76 Table 3. Types of Autoimmune Hepatitis* Autoimmune hepatitis Features Type 1 Type 2 Type 3 Characteristic autoantibodies ANA, SMA Anti-LKM1 Anti-SLA/LP Associated autoantibodies panca, antiactin, anti-asgpr Anti-LC1, anti-asgpr ANA, SMA, anti-asgpr Age onset All ages 2 to 14 y All ages Common concurrent immune Autoimmune thyroiditis, ulcerative Vitiligo, type 1 diabetes Same as type 1 diseases colitis, synovitis mellitus, autoimmune thyroiditis, APS1 Implicated genetic factors DRB1*0301 (Northern European), HLA-B14, HLA-DR3, Uncertain DRB1*0401 (Northern European), C4A-QO, DRB1*07 DRB1*1501 (protective), DRB1*0404 (Mexican), DRB1*0405 (Japanese), DRB*1301 (Argentine, Brazilian) Autoantigen Uncertain P-450 IID6 (CYP2D6), trnp (Ser)Sec P-450 IA2 (APS1), P-450 IA6 (APS1) Treatment Corticosteroids Corticosteroids Corticosteroids *Anti-ASGPR = antibodies to asialoglycoprotein receptor; anti-lc1 = antibodies to liver cytosol type 1; anti-sla/lp = antibodies to soluble liver antigen/liver pancreas; APS1 = autoimmune polyglandular syndrome type 1; panca = perinuclear antineutrophil cytoplasmic antibodies; trnp (Ser)Sec = transfer ribonucleic acid protein complex for selenoprotein. The remaining abbreviations are explained in the footnote to Table 1. drial antibodies in the clinical laboratory. Antimitochondrial antibodies react against the parietal cells of the murine stomach and the distal tubules of the murine kidney. 48,51 An exuberant reactivity against the kidney tubules can obscure distinctions between the renal patterns of indirect immunofluorescence and confuse the diagnosis. Previous studies have indicated that 27% of patients with autoimmune hepatitis and antimitochondrial antibodies actually have anti- LKM1. 63 A greater understanding of the potential for confusion between serologic patterns and the availability of ELISA based on recombinant antigens should prevent these misclassifications. Type 2 autoimmune hepatitis is predominantly a disease of children (age, 2-14 years) (Table 3). 62 Among Caucasoid North American adults with autoimmune hepatitis, only 4% have anti-lkm1. 63 Conversely, in Europe, 20% of patients with the diagnosis of type 2 autoimmune hepatitis are adults. 62 The basis for geographical and ethnic variations in disease distribution is unknown but may reflect differences in etiologic factors and/or genetic predispositions. Type 2 autoimmune hepatitis is the only form of the disease in which the target autoantigen has been defined: the cytochrome monooxygenase P-450 IID6 (CYP2D6), an important drug-metabolizing enzyme. 31,32 Antibodies to LKM1 react to a short linear epitope on the recombinant antigen 32 ; anti-lkm1 inhibit enzyme activity in vitro, 64 and antigen- and disease-specific liver-infiltrating lymphocytes have been isolated from patients with the disease. 65 An animal model based on this autoantigen must be developed to establish pathogenic relationships. 66 Patients with type 2 autommune hepatitis have a high frequency of concurrent autoimmune diseases, especially type 1 diabetes mellitus, vitiligo, and autoimmune thyroiditis (Table 3). 62 They also commonly have organ-specific autoantibodies, such as antibodies to parietal cells, islets of Langerhans, and thyroid. Low serum concentrations of IgA have been reported in patients with type 2 autoimmune hepatitis, as well as a higher frequency of progression to cirrhosis compared with patients with type 1 autoimmune hepatitis. 62 These 2 last-mentioned distinctions have not been well established, and recent studies have indicated that type 2 autoimmune hepatitis responds as well to corticosteroids as does type 1 disease. 67 Like type 1 autoimmune hepatitis, an acute, occasionally fulminant, presentation has been recognized, and treatment must be prompt. 68 Type 2 autoimmune hepatitis is present in 15% of patients with the autoimmune polyglandular syndrome type 1 (APS1). 33,34 This syndrome is characterized by ectodermal dysplasia, mucocutaneous candidiasis, and multiple endocrine organ failure (parathyroid, ovarian, and adrenal). A single gene defect on chromosome 21q22.3 has been identified as the basis for the syndrome, and the disease is inherited in mendelian fashion. The APS1 gene encodes for a transcription factor called the autoimmune regulator, which is expressed in epithelial and dendritic cells within the thymus. This autoimmune regulator modulates clonal

5 Mayo Clin Proc, December 2001, Vol 76 Autoimmune Hepatitis 1241 deletion of autoreactive T cells and can affect self-tolerance. The target autoantigens associated with APS1 are P- 450 IA2 and P-450 IA6. Unlike other autoimmune diseases, APS1 has complete penetrance of the susceptibility gene, no HLA-DR associations, and no female predominance. It is an important condition to recognize because APS1 has been associated with an aggressive liver disease that responds poorly to corticosteroid therapy. Inadvertent inclusion of patients with APS1 in descriptions of type 2 autoimmune hepatitis can distort perceptions of the natural history and prognosis. Antibodies to LKM1 have been recognized in as many as 10% of patients with chronic hepatitis C. 32,69 These antibodies react to diverse epitopes on recombinant P-450 IID6 (CYP2D6) and differ from the anti-lkm1 found in classic type 2 autoimmune hepatitis. 69,70 In the latter instance, reactivity is restricted to a core motif between positions on the recombinant molecule. Homologies have been described between recombinant P-450 IID6 (CYP2D6) and the genome of the hepatitis C virus. 32 This molecular mimicry may result in cross-reacting antibodies in some patients. Analyses of the viral genomic sequences in patients with and without anti-lkm1 have not indicated a virusspecific basis for the autoantibodies, and a host-specific genetic predisposition for autoantibody expression is likely. 71,72 Antibodies to liver cytosol type 1 (anti-lc1) were originally described in uninfected patients with anti-lkm1, and they were considered adjunctive markers of the disease that reinforced the diagnosis of type 2 autoimmune hepatitis. 73 Subsequently, anti-lc1 were ascribed a prognostic importance because of their frequency in young patients with severe inflammatory activity. 74 The clinical implications of anti-lc1 have been challenged by reports indicating their frequent absence in children with type 2 autoimmune hepatitis, their lack of association with fulminant disease, and their occurrence in patients with hepatitis C virus infection and those with primary sclerosing cholangitis. 75 Formiminotransferase cyclodeaminase 38 and argininosuccinate lyase 39 have been proposed as antigenic targets. Serum levels of anti-lc1 fluctuate with inflammatory activity in contrast to anti-lkm1, and anti-lc1 may ultimately prove useful as markers of residual hepatocellular inflammation or as probes of an autoantigen associated with disease severity. 76 Type 3 Type 3 autoimmune hepatitis is the least established form. It is characterized by the presence of antibodies to soluble liver antigen/liver pancreas (anti-sla/lp). 77,78 These antibodies have high specificity for autoimmune hepatitis, and a 50-kD cytosolic protein has been identified as the target autoantigen. 79 The identity of this protein is unestablished, but a transfer RNA complex responsible for incorporating selenocysteine into peptide chains is a leading candidate. 80 Patients with anti-sla/lp are indistinguishable from patients with classic type 1 autoimmune hepatitis by age, sex distribution, frequency and nature of other autoantibodies, and responsiveness to corticosteroid therapy. 81,82 Therefore, the presence of anti-sla/lp does not define a clinically distinct subgroup, and the autoantibodies may be markers of a subgroup of patients with type 1 autoimmune hepatitis who have more severe disease and/ or greater propensity for relapse after corticosteroid withdrawal than their seronegative counterparts. 83,84 The most important clinical application of testing for anti-sla/lp may be to reclassify patients with cryptogenic chronic hepatitis as having autoimmune hepatitis. Indeed, seropositivity can be demonstrated in 26% of patients who lack conventional markers. 81 A commercial ELISA for anti- SLA/LP is available in Europe, and experience with this assay will grow. 83,84 GENETIC PREDISPOSITIONS Type 1 autoimmune hepatitis has a strong genetic predisposition. Among Caucasoid Northern Europeans and North Americans, susceptibility resides within the DRB1 gene. 85,86 DRB1*0301 is the principal susceptibility allele, and DRB1*0401 is a secondary but independent risk factor (Table 3). 87 Of patients with type 1 autoimmune hepatitis, 85% have DRB1*0301, DRB1*0401, or both. DRB1*0301 and DRB1*0401 also affect clinical expression and behavior. Patients who have DRB1*0301 are younger, and their response to corticosteroid therapy is poor compared with patients who have DRB1* Remission occurs less frequently, 88 treatment failure occurs more often, 88 relapse after drug withdrawal is more common, 89 and death from hepatic failure or requirement for liver transplantation is more frequent in these patients. 88,90 In contrast, patients with DRB1*0401 are older, are often women, have a greater occurrence of other immune diseases, and have a higher frequency of remission during corticosteroid treatment. 88,91 The effect of these alleles on clinical features and outcome is reflected in the experience from Japan. The Japanese population has a low prevalence of DRB1*0301, and the autoimmune hepatitis in this population is typically associated with HLA-DR4. 19,92 These patients are older, have milder disease, and respond better to corticosteroids than do Caucasoid patients with HLA-DR3 reported from elsewhere. The basis for the genetic effects on susceptibility, expression, and behavior of type 1 autoimmune hepatitis is uncertain. The leading hypothesis is that susceptibility re-

6 1242 Autoimmune Hepatitis Mayo Clin Proc, December 2001, Vol 76 lates to the amino acid sequences encoded by DRB1*0301 and DRB1*0401 in the antigen-binding groove of class II major histocompatibility complex (MHC) antigens These antigens present the antigenic peptide to CD4 helper T cells, and the ability of this complex to activate the immunocytes affects the vigor of the immune response and the occurrence of disease. Analyses of amino acid sequence variations encoded by the susceptibility alleles of type 1 autoimmune hepatitis indicate that the risk of disease relates to a 6 amino acid sequence between positions 67 and 72 of the DRβ polypeptide chain of the class II MHC molecule. 86,87 Lysine at position DRβ71 is located at the lip of the antigenbinding groove, and it is the critical contact point between the antigenic peptide, the antigen-binding groove of the class II MHC molecule, and the T-cell antigen receptor of the CD4 helper T cells. Multiple alleles encode lysine at DRβ71, and therefore many alleles may contribute to disease susceptibility and outcome through a dosing effect. Patients with 3 or 4 alleles encoding lysine at DRβ71 have a poorer response to corticosteroid therapy than do patients with 1 or no alleles encoding lysine at this position. 88 DRB1*1501 protects against type 1 autoimmune hepatitis in Caucasoid patients, and it encodes an isoleucine for a leucine at position DRβ67. 86,87 More importantly, it encodes an alanine for a lysine at position DRβ71. Alanine is a negatively charged, structurally dissimilar molecule to the positively charged lysine, and its substitution for lysine would alter the antigen binding characteristics of the class II MHC molecule. In this fashion, a single amino acid substitution at a critical site could affect disease occurrence and outcome. Not all patients with type 1 autoimmune hepatitis have the same susceptibility alleles, and not all patients with the same susceptibility alleles have the same clinical expressions. 97 The susceptibility alleles among mestizo Mexicans (DRB*0404), 17 Japanese (DRB1*0405), 19,92 and South Americans (DRB*1301) differ from those of Caucasoid North Americans and Northern Europeans (Table 3). These observations have generated a shared motif hypothesis that states that disease risk relates to the amino acid sequences encoded in the antigen-binding groove of the class II MHC molecules The critical motif must be a short sequence, and multiple alleles must encode the same or similar critical sequence. In this fashion, diverse alleles can affect susceptibility, and their individual predominance among certain ethnic groups and/or geographical areas may reflect selection by indigenous yet undefined etiologic agents. DRB*0404 and DRB*0405 have encoding characteristics that support the shared motif hypothesis, whereas DRB*1301 does not. The autoimmune promoter hypothesis has been developed to evaluate the basis for differences in clinical expression and outcome among patients with the same or no class II susceptibility alleles This hypothesis states that nonspecific promoters within and outside the MHC can influence disease occurrence and behavior alone or in synergism with each other or the known risk factors. Female sex is an example of a nonspecific autoimmune promoter that may affect disease occurrence through estrogen effects, associations with HLA-DR4, cytokine profiles, and/or microchimerisms arising from childbearing. 101,102 In type 1 autoimmune hepatitis, a polymorphism involving substitution of an adenine for a guanine at position 308 of the tumor necrosis factor α gene (TNFA*2) is associated with early disease onset, DRB1*0301, and poor response to therapy. 103,104 Similarly, a guanine for alanine substitution at position 49 of the first exon of the cytotoxic T-lymphocyte antigen 4 gene (CTLA-4) may increase immune responsiveness by failing to dampen immunocyte activation. 105 Polymorphisms of the Fas gene may also contribute by limiting apoptosis and prolonging the survival of activated immune cells. 106 Other nonspecific autoimmune promoters undoubtedly exist that affect antigen presentation, immunocyte activation, cytokine production, and fibrosis in individual patients, and future studies must fully define their nature and interactions. The genetic basis for type 2 autoimmune hepatitis has not been established. Early reports described an association with HLA-B14, HLA-DR3, and C4A-QO, 107 but more recent studies using high-resolution DNA-based techniques have implicated DRB1*07 as a risk factor in Brazilian 100 and white German 108 patients. PATHOGENIC MECHANISMS Two mechanisms of liver cell injury have been implicated in autoimmune hepatitis, and both may be important at different stages of the disease. 4,94,95,109 A cell-mediated cytotoxicity implies differentiation of activated CD4 helper T cells into cytotoxic T lymphocytes. These effectors then accomplish liver cell destruction through the release of lymphokines. A type 1 cytokine milieu consisting mainly of interleukin (IL)-2, IL-12, and tumor necrosis factor α modulates this response. The demonstration of antigensensitized, disease-specific cytotoxic T lymphocytes within the liver tissue of patients supports this mechanism. 65 A cell-mediated, antibody-dependent cytotoxicity has also been described in which the poorly modulated production of IgG by plasma cells results in antigen-antibody complexes on the hepatocyte membrane surface. 4,94,95,109 These aggregates are then targeted by the Fc receptors of natural killer cells, which cause cytolysis. A type 2 cytokine response modulates this pathway, and IL-4 and

7 Mayo Clin Proc, December 2001, Vol 76 Autoimmune Hepatitis 1243 Table 4. Treatment Indications* Absolute Relative None Serum AST 10-fold times Symptoms (fatigue, arthralgia, No symptoms and mild interface upper limit of normal jaundice) or portal hepatitis Serum AST 5-fold times upper Serum AST and/or γ-globulin Inactive cirrhosis limit of normal and γ-globulin < absolute criteria level twice normal Bridging necrosis or multilobular necrosis in liver tissue Interface hepatitis Decompensated inactive cirrhosis *AST = aspartate aminotransferase. IL-10 are the principal mediators. This hypothesis has been supported by demonstration of antigen-antibody aggregates on the hepatocyte surface 110 and overexpression of IL-10 in some patients. 111 Both pathways are modulated by cytokines that are interactive and cross-regulatory. Studies based on isolated cell populations from the liver and serum levels of cytokines in untreated patients with type 1 autoimmune hepatitis have suggested that a type 2 cytokine response predominates and that the cell-mediated, antibody-dependent form of cytotoxicity is common Other investigations have indicated that the type 2 cytokine response may be part of a recovery phase and associated with convalescence from a cell-mediated injury. 115 The dynamic interrelationships between both pathogenic pathways are uncertain, and they must be unraveled before the disease process can be understood and manipulated by site-specific therapeutic interventions. TREATMENT INDICATIONS The absolute and relative indications for treatment are based on clinical experiences from controlled treatment trials and long-term surveillance programs. 2-4, Patients with the most severe disease by clinical, laboratory, and histological indices have the poorest prognosis and greatest requirement for treatment. Retrospective analyses indicate that the 3-year survival of untreated patients with severe disease is 50%, and the 10-year survival is 10%. 119 Prospective studies indicate that mortality in this group is as high as 40% within 6 months. 120 In contrast, patients with mild disease have normal 5-year survival expectations, and their risk of cirrhosis is no greater than 17% without treatment. 121,122 In these latter patients, the benefit-risk ratio of therapy may be too low to justify treatment. Based on controlled clinical trials, the absolute indication for treatment is sustained severe hepatic inflammation (Table 4). 120,123,124 Manifestations include symptoms of fatigue, arthralgia, and/or jaundice; serum aspartate aminotransferase (AST) levels of at least 10-fold times normal; serum AST levels of at least 5-fold times normal in conjunction with serum γ-globulin levels greater than 2-fold times normal; and/or histological changes of bridging necrosis or multilobular collapse. The relative indications for treatment are symptoms of easy fatigability, serum AST and/or γ-globulin levels less than those with the severe degree, and histological features of interface hepatitis (Table 4). 121,122,125 Patients with inactive cirrhosis, portal or mild interface hepatitis, and no symptoms or decompensated inactive cirrhosis with ascites, encephalopathy, and/ or gastrointestinal bleeding do not require immunosuppressive therapy (Table 4). All age groups can be affected by autoimmune hepatitis, and indications for therapy are the same for children and elderly patients. Children may have the clinical phenotype of autoimmune hepatitis and cholangiographic changes of primary sclerosing cholangitis. 67,126 These patients with autoimmune sclerosing cholangitis infrequently have inflammatory bowel disease or features of cholestasis, and they respond well to corticosteroids. Consequently, their indications for treatment are similar to those for children with classic disease. Postmenopausal women respond as well to initial corticosteroid therapy as their premenopausal counterparts, and they should be treated as vigorously in accordance with the same guidelines for therapy. 127 Remission (81% vs 83%; P=.9) and treatment failure (7% vs 7%) occur as commonly in these patients as in others, and such patients have a 5- year survival (97% vs 92%; P=.2) that is indistinguishable from that of younger counterparts who are treated similarly. The frequency of adverse effects during initial therapy is also comparable between these groups (49% vs 33%; P=.1), and this risk should not affect the initial management decision or treatment regimen. TREATMENT REGIMENS Prednisone alone or a lower dose of prednisone in combination with azathioprine is effective in the treatment of all forms of autoimmune hepatitis. 67, Either regimen induces clinical, laboratory, and histological remission in 65% of patients within 18 months. Most importantly, either schedule enhances survival expectations. The life expectancy of treated patients exceeds 80% after 20 years of

8 1244 Autoimmune Hepatitis Mayo Clin Proc, December 2001, Vol 76 Table 5. Treatment Regimens* Regimen Daily doses Relative contraindications Combination Severe cytopenia, TMT Prednisone (mg) 30 for 1 wk deficiency, pregnancy, 20 for 1 wk active neoplasm 15 for 2 wk 10 for maintenance Azathioprine (mg) 50 for maintenance Prednisone alone (mg) 60 for 1 wk Obesity, osteopenia, 40 for 1 wk emotional lability, brittle 30 for 2 wk diabetes, labile hypertension, 20 for maintenance postmenopausal state, acne *TMT = thiopurine methyltransferase. observation and does not differ from that of age- and sexmatched normal controls from the same geographical region. 27 Progression to cirrhosis occurs in as many as 40% of patients within 10 years despite therapy, but this histological finding does not affect immediate prognosis. 26,27 Furthermore, the risk of hemorrhage from esophageal varices may be reduced with corticosteroid therapy. 124,128 The preferred treatment schedule is prednisone in combination with azathioprine (Table 5). 129 The combination schedule facilitates use of a lower dose of prednisone and is associated with fewer corticosteroid-related adverse effects. It is especially useful in patients with obesity, acne, labile hypertension, brittle diabetes, emotional lability, and/or osteopenia. The prednisone alone schedule is useful in patients with severe, preexistent cytopenia, pregnancy or contemplation of pregnancy, deficiency of thiopurine methyltransferase, or active malignancy. It also can be used in patients with relative treatment indications in whom treatment duration will be 6 months or less. The advantages of the corticosteroid-sparing combination regimen become apparent only after 12 months of therapy. The preferred treatment regimens for children are similar to those for adults but have been established less rigorously Prednisone is the principal medication and is usually given in a dose of 2 mg/kg daily (up to 60 mg/d). Because of the potentially deleterious effects of corticosteroids on linear growth, bone development, and physical appearance in children, tapering regimens or alternate-day schedules are commonly used. Alternate-day schedules of corticosteroids do not induce histological remission in adults, and thus this approach is no longer used as initial treatment in this group. 129 The alternate-day regimen may counterbalance the benefits and risks of corticosteroid therapy for children and is widely used in this population. Azathioprine or 6-mercaptopurine can also be introduced early as a corticosteroid-sparing measure. Regimens incorporating cyclosporine as initial treatment followed by prednisone and azathioprine have been well tolerated and effective in children, 133,134 but before such regimens can be advocated, their advantages over traditional therapies must be fully demonstrated. Elderly patients should receive the same treatment schedule as younger adults, and they are ideal candidates for the combination regimen (Table 5). 127 The frequencies of vertebral compression (23% vs 7%; P=.05) and osteopenia (85% vs 22%; P<.002) are higher in postmenopausal women only after protracted therapy or re-treatment after relapse. Elderly patients also experience a higher cumulative frequency of adverse effects (77% vs 48%; P<.01) and a greater occurrence of multiple toxicities (44% vs 13%; P<.01) under these circumstances. 127 Consequently, modifications in the long-term management strategy are necessary in this group, and empirical regimens with prednisone in doses titrated to less than 10 mg/d or azathioprine in doses of 2 mg/kg daily are appropriate if the duration of treatment exceeds 1 year or re-treatment after relapse is required. Liver transplantation is effective in the treatment of decompensated disease unresponsive to conventional therapies. 90 The 5-year survival of patient and graft ranges from 83% to 92%, and the actuarial 10-year survival after transplantation is 75%. 135,136 Disease recurrence is common (17%) 137 but is typically mild and managed by adjusting the immunosuppressive regimen. 13, Progression to cirrhosis and graft failure are possible, and patients should be monitored closely, especially if corticosteroids are discontinued after transplantation. 141, Patients with recurrent disease typically have HLA-DR3 and/or HLA-DR4, but recurrence is not related to a mismatch of these markers between donor and recipient. 128 Importantly, no findings at presentation predict prognosis and need for transplantation. The decision to perform transplantation should be made after a corticosteroid treatment trial. Failure of the serum bilirubin level to improve after 2 weeks of corticosteroid therapy in a patient with multilobular necrosis is invariably associated with death. 147 Similarly, death is common in

9 Mayo Clin Proc, December 2001, Vol 76 Autoimmune Hepatitis 1245 Table 6. Treatment End Points and Appropriate Response* End point Definition Response Remission No symptoms, AST 2-fold times normal Tapered withdrawal of prednisone over 6 wk; limit, normal liver tissue, portal hepatitis, determine serum AST, bilirubin, and γ-globulin or inactive cirrhosis levels every 3 wk for 3 mo, then every 6 mo for 1 y, then annually Treatment AST and/or bilirubin level >66% of earlier Prednisone, 60 mg/d, or prednisone, 30 mg/d, failure values, increased histological activity, with azathioprine, 150 mg/d, for at least 1 mo; and/or clinical worsening despite then reduce dose of prednisone by 10 mg each compliance with therapy month and azathioprine by 50 mg each month until maintenance levels are achieved; 6-mercaptopurine, 1.5 mg/kg daily, can be used in place of azathioprine; liver transplantation if recalcitrant clinical decompensation Drug Intolerable obesity or cosmetic changes, Dose reduction of 50%; complete withdrawal if toxicity psychosis, osteoporosis with symptomatic no improvement with dose reduction or toxicity bone disease, brittle diabetes, or peptic is severe; treatment with tolerated agent only; ulceration during prednisone therapy; 6-mercaptopurine, 1.5 mg/kg daily, may be progressive cytopenia, cholestatic liver tolerated better than azathioprine disease, nausea and vomiting, neoplasm, or rash during azathioprine therapy *AST = aspartate aminotransferase. patients who develop ascites after 4 years of continuous treatment without remission. 90 ADJUNCTIVE THERAPIES Adjunctive therapies can prevent or minimize the adverse effects associated with autoimmune hepatitis and its treatment. They should include a regular exercise program (walking, swimming, or biking) and conservative dietary restrictions that stabilize weight. Vitamin supplementation, including vitamin K for hypoprothrombinemia (10 mg/d), calcium (1-1.5 g/d), and vitamin D (50,000 U once each week), is appropriate. Hormonal replacement therapy should be considered for postmenopausal women, and symptomatic osteoporosis or progressive osteopenia diagnosed by bone densitometry should be treated with physical therapy and bisphosphonates, such as alendronate, 10 mg/d, 148 or etidronate, 400 mg/d, for 14 days every 3 months. 149 Patients receiving long-term corticosteroid treatment should be monitored for bone disease by annual bone mineral densitometry of the lumbar spine and hip. 150 Standard health maintenance issues should be emphasized throughout follow-up, including avoidance of alcohol and tobacco, weight and lipid control, and adherence to screening protocols for prevention of lung, breast, pelvic, and colonic cancer. TREATMENT END POINTS Treatment is continued until remission, treatment failure, or drug toxicity. 2-4, Remission implies disappearance of symptoms, resolution of laboratory abnormalities except for a less than 2-fold elevation of the serum AST level, and improvement of histological findings to normal, near normal, or inactive cirrhosis (Table 6). Histological improvement lags behind clinical and laboratory improvement by 3 to 6 months, and treatment should be continued for at least this duration. 120,151 Examination of liver tissue is the only method for establishing remission of disease, and it should be considered before termination of therapy. Restoration of the hepatic architecture to normal is associated with a 20% frequency of relapse after drug withdrawal. 152 The presence of portal hepatitis at termination of treatment is associated with a 50% frequency of relapse, and progression to cirrhosis or persistence of interface hepatitis is associated with an 86% to 100% frequency of relapse. Liver biopsy can grade the adequacy of the histological response, the risk of subsequent relapse, and the need for additional treatment before drug withdrawal. 152 Treatment failure indicates deterioration during therapy (Table 6) and occurs in 13% of patients. 2-4, Its recognition justifies termination of conventional drug schedules and institution of high-dose regimens. High-dose prednisone alone (60 mg/d) or a lower dose (30 mg/d) in conjunction with azathioprine (150 mg/d) induces laboratory remission in more than 60% of patients within 2 years. 153 Histological remission, however, is achieved in only 20%. Patients in whom conventional therapy fails are at risk of drug-related complications and/or liver transplantation. The active metabolite of azathioprine is 6-mercaptopurine, and it may have greater immunosuppressive action than the parent drug, possibly because of greater intestinal absorp-

10 1246 Autoimmune Hepatitis Mayo Clin Proc, December 2001, Vol 76 tion and/or different metabolic pathways. 154 Because of its successful use in a small number of patients with treatment failure (1.5 mg/kg daily), 6-mercaptopurine has been recommended as empirical treatment. Drug toxicity requires premature discontinuation of therapy (Table 6) in 13% of patients. 2-4, The most common reason for drug withdrawal or dose reduction is the development of intolerable obesity or cosmetic changes (47%). Osteoporosis with vertebral compression (27%), brittle diabetes (20%), and peptic ulceration (6%) also preclude continuation of conventional therapy. 155 Cytopenia, hepatotoxicity, rash, and gastrointestinal upset associated with azathioprine therapy are rare justifications for dose adjustments. Drug-related adverse effects can improve with dose reduction, and a 50% decrease in dose is the first course of action. An inability to reverse the complication within 1 month necessitates termination of treatment. Severe reactions, including psychosis, extreme cytopenia, and symptomatic osteopenia with or without vertebral compression, justify immediate discontinuation of the offending agent. In such instances, therapy with the tolerated agent can frequently be maintained with an adjusted dose to control disease activity. Treatment with azathioprine (2 mg/kg daily) is an option in patients intolerant of corticosteroids. RELAPSE Relapse indicates recrudescence of disease activity after drug withdrawal and is characterized by an increase in the serum AST level to at least 3-fold times normal. 120,151,152, Previous studies have demonstrated that this degree of change in the serum AST concentration correlates closely with the presence of interface hepatitis on histological examination. 151 Liver biopsy is unnecessary to document this outcome. Relapse is most common during the first 6 months after termination of therapy (50%), and its frequency decreases with increasing duration of sustained remission. The probability of relapse after 1 year of sustained remission is 8%. Relapse requires re-treatment with the original drug schedule. A rapid response to re-treatment can be anticipated, and patients typically experience another remission. 156 Prior relapse identifies patients prone to relapse again, and this consequence can be anticipated in most patients who experience a second remission and therapy is withdrawn. The decision of drug withdrawal after a second remission is based on an understanding of the benefit-risk ratio of repeated relapse and re-treatment. 155 Patients who experience relapse and require re-treatment have higher frequencies of progression to cirrhosis (40% vs 18%) and death from liver failure (15% vs 4%) compared with patients who sustain remission; however, these differences have not been statistically significant. The major consequence of relapse and re-treatment is the development of drug-related complications (59% vs 29%; P<.05). 155 The frequency of adverse effects after initial therapy is 29%, similar to that after the first relapse and re-treatment (33%). 155 Subsequent relapses and re-treatments are associated with a complication frequency of 70%. In contrast, the probability of sustained remission diminishes after each relapse to as low as 14%. Benefit-risk analyses justify alternative management strategies after 2 relapses; however, treatment adjustments are often made after the first relapse, especially if complete histological resolution had been achieved before the relapse. Patients who have experienced relapse several times require treatment with long-term, low-dose prednisone or azathioprine administered indefinitely. The low-dose prednisone strategy requires a careful reduction in the daily maintenance dose of prednisone until the lowest level is achieved to prevent symptoms and maintain serum AST levels lower than 5-fold times normal. 159 Overall, 87% of patients can be managed on 10 mg/d or less of prednisone (median dose, 7.5 mg/d). Adverse effects associated with earlier conventional treatments improve or disappear in 85% of patients; new adverse effects do not develop, and survival is unaffected. Indefinite administration of azathioprine requires induction of clinical and laboratory remission by conventional treatments. 158,160 The corticosteroid component of therapy is withdrawn, and the dose of azathioprine is increased to 2 mg/kg daily. Azathioprine is then used as the sole drug indefinitely. With this approach, 87% of adult patients remain in remission during a median observation interval of 67 months. Follow-up liver biopsies have shown inactive or minimal histological disease in 94% of patients; corticosteroid-related adverse effects have improved or disappeared in most patients, and the drug is generally well tolerated. The most common adverse effects are withdrawal-induced arthralgias (63%), lymphopenia (57%), and myelosuppression (7%). Neoplasm develops in 8% of patients; however, cell types have been diverse, and their frequencies have not been compared to age-matched controls. Long-term prednisone and azathioprine strategies for relapse have not been compared head-to-head in adults, and no objective basis exists for preference. PROMISING TREATMENTS New immunosuppressive agents promise greater blanket immunosuppression compared with prednisone or azathioprine (Table 7). 66 These agents have emerged mainly from the transplantation arena, and their application in autoimmune hepatitis has been empirical. The most exciting new

11 Mayo Clin Proc, December 2001, Vol 76 Autoimmune Hepatitis 1247 Table 7. Promising New Immunosuppressive Drugs* Drug Dose Actions Cyclosporine 5-6 mg/kg daily Inhibits release of soluble lymphokines, suppresses clonal expansion of activated helper T cells Tacrolimus 3 mg twice daily Inhibits expression of IL-2 receptor, inhibits generation of cytotoxic T cells Mycophenolate 1 g twice daily Inhibits inosine monophosphate mofetil dehydrogenase and DNA synthesis, impairs lymphocyte proliferation Ursodeoxycholic mg/kg daily Replaces hydrophobic bile acids, acid alters class I HLA expression, inhibits IL-2, IL-4, and interferon γ, impairs nitric oxide production and apoptosis Budesonide 3 mg thrice daily Second-generation corticosteroid, high first-pass clearance, low systemic availability, metabolites lack glucocorticoid activity *IL = interleukin. drug is mycophenolate mofetil, which has actions similar to azathioprine but with greater lymphocyte specificity. Mycophenolate mofetil inhibits inosine monophosphate dehydrogenase which in turn restricts DNA synthesis and lymphocyte proliferation. In a treatment trial of 7 patients in whom conventional therapies had failed or had been poorly tolerated, biochemical remission and histological improvement were achieved in 5 patients after treatment with 1 g twice daily for 7 months. The only adverse effect was a single episode of leukopenia that required dose adjustment. 161 Cyclosporine, tacrolimus, budesonide, and ursodeoxycholic acid are other candidate therapies (Table 7). Experiences with cyclosporine and tacrolimus 166 have been anecdotal but supportive of their consideration in patients who have resistance or intolerance to corticosteroids. Cyclosporine has also been advocated as initial therapy for pediatric and adult patients. 133,134 Budesonide 167 and ursodeoxycholic acid 168 have been ineffective as adjunctive or replacement therapy for patients dependent on corticosteroid treatment. However, these drugs may have a role in treatment-naive patients with mild disease. 169,170 Controlled clinical trials are needed before the current management strategies can be altered. Site-specific interventions are now feasible because pathogenic mechanisms are being defined (Table 8). 66,171 These therapies are mainly theoretical, and confident animal models must be developed before consideration in clinical trials. Peptides that competitively inhibit the display of autoantigens in the antigen-binding groove of MHC molecules have been considered in autoimmune diabetes and are feasible in autoimmune hepatitis. 172 Full characterization of the autoantigens responsible for the disease is necessary to promote this intervention. Soluble CTLA-4 may be a means to modulate the activation of CD4 helper T cells in a site-specific fashion, 173,174 and T-cell vaccination has been shown in animal models to prevent disease and decrease activity as effectively as corticosteroid treatment. 175 Clarification of the effector clone is required to ensure precise targeting of the vaccine. Cytokine manipulations become feasible as the dominant cytokine profile associated with disease activity is clarified. Antibodies to tumor necrosis factor α have the promise of down-regulating a type 1 cytokine response, and IL-10 therapy may favor convalescence by counterregulating cytokines promoting a cytotoxic T-cell response. 66 Oral tolerance regimens have promise in autoimmune hepatitis because tolerance depends on hepatic portal circulation and antigen uptake by immunocytes residing within the liver. 176,177 Oral tolerance implies induction of systemic nonresponsiveness to a fed antigen, and it has been used in the prevention and treatment of experimental animal models of autoimmune disease as well as in clinical trials of patients with multiple sclerosis, rheumatoid arthritis, juvenile rheumatoid arthritis, inflammatory uveitis, autoimmune thyroiditis, and type 1 diabetes mellitus. Efficacy depends on the antigen form, antigen dose, and timing of antigen administration, and further studies are necessary to refine these details. Gene therapy may deliver immunoregulatory or regenerative growth factors that correct or counterbalance disturbances that perpetuate or enhance autoreactivity. 178 LONG-TERM SURVEILLANCE Follow-up must be lifelong to assess progression to cirrhosis, late relapse, and/or malignant transformation. Usually, annual physical examinations, laboratory assessments, and