Bile ductal injury and ductular reaction are frequent phenomena with different significance in autoimmune hepatitis

Worse fibro-inflammatory activity on diagnostic liver biopsy adversely impacts biochemical remission in autoimmune hepatitis

BACKGROUND

Autoimmune hepatitis (AIH) patients can present with advanced fibrosis at diagnosis or may progress to the same if biochemical remission on treatment is not achieved.

METHODS

We conducted a single-center retrospective analysis of 34 pediatrics and 39 adult AIH patients. Three pathologists, blinded to clinical information, reviewed the diagnostic liver biopsy (DLB) slides of AIH patients. We evaluated the impact of clinical, laboratory, and histopathologic parameters on outcomes including biochemical remission (BR).

RESULTS

Incidence of advanced (Ludwig stage 3 or 4) fibrosis on DLB was 45.2 %. AIH patients with advanced fibrosis had higher median Ishak score (p < 0.001) and higher IgG level (p = 0.01) at diagnosis. The incidence of BR at 6-month (31.2% vs. 88.6 %, p = 0.001) and 1-year (68.8% vs. 88.6 %, p = 0.04) post-diagnosis was significantly lower in AIH patients with advanced fibrosis. Although not statistically significant, a higher proportion of AIH patients with advanced fibrosis were on high dose of steroids (58% vs. 37.9 %, p = 0.1) at 1 year post diagnosis. Higher serum IgG level at diagnosis was associated with lower odds of achieving BR at 6-month (p = 0.004) and 1-year (p = 0.03) post-diagnosis in multivariate analysis. Pediatric age at diagnosis (p = 0.02) was associated with higher steroid dose at 1-year post-diagnosis in univariate analysis.

CONCLUSIONS

Findings of advanced fibrosis on DLB of AIH patients was accompanied by more pronounced necro-inflammatory activity and higher serum IgG level, which translated to lower rates of BR and higher exposure to steroids during the first year after diagnosis.

The phenotypic landscape of primary biliary cholangitis and autoimmune hepatitis variants

Autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) stand as distinct diseases, yet occasionally intertwine with overlapping features, posing diagnostic and management challenges. This recognition traces back to the 1970s, with initial case reports highlighting this complexity. Diagnostic scoring systems like IAIHG and simplified criteria for AIH were introduced but are inherently limited in diagnosing variant syndromes. The so-called Paris criteria offer a diagnostic framework with high sensitivity and specificity for variant syndromes, although disagreements among international guidelines persist. Histological findings in AIH and PBC may exhibit overlapping features, rendering histology alone inadequate for a definitive diagnosis. Autoantibody profiles could be helpful, but similarly cannot be considered alone to reach a solid and consistent evaluation. Treatment strategies vary based on the predominant features observed. Individuals with overlapping characteristics favoring AIH ideally benefit from corticosteroids, while patients primarily manifesting PBC features should initially receive treatment with choleretic drugs like ursodeoxycholic acid (UDCA).

Histopathology and its clinical correlation of liver biopsy in patients with treated autoimmune hepatitis

The diagnosis of autoimmune hepatitis (AIH) relies on well-established criteria encompassing histological, serological, and clinical features. Diagnosing AIH may become challenging when encountering patients who have undergone steroid therapy for other co-existing diseases. Thirty-nine liver biopsies from 25 patients with treated and untreated AIH were classified into three groups: 1) Newly diagnosed untreated biopsies (n = 16); 2) Newly diagnosed partially treated biopsies from patients already on steroid treatment for other co-existing diseases (n = 9); 3) Previously diagnosed biopsies from patients who had undergone complete treatment (n = 14). In the untreated AIH group, at least 50 % of the cases exhibited the following features: at least moderate portal inflammation (81 %), at least moderate lobular inflammation (56 %), ductular reaction (94 %), inflammation gradient from bile duct to interface (88 %), unequivocal interface hepatitis (100 %), emperipolesis (56 %), plasma cell cluster (88 %), apoptosis or necrosis (63 %), pericentral inflammation (63 %), and periportal fibrosis (88 %). Although all these diagnostically sensitive histologic features were present in significantly fewer cases after treatment (p < 0.05), the features of ductular reaction, inflammation gradient from bile duct to interface, pericentral inflammation, and periportal fibrosis were likely to persist after treatment, especially in partially treated cases; these features did not show a significant association with higher transaminase levels (P > 0.05) and were considered as indirect features of hepatocytic injury. Our data suggest categorizing AIH histological features into direct and indirect hepatocytic injuries. Direct hepatocytic injury features significantly correlate with transaminase levels and respond well to treatment, while indirect ones show weaker transaminase correlation and relative treatment resistance.

Selective inhibition of hepatic stellate cell and fibroblast-derived LOXL1 attenuates BDL- and Mdr2-/--induced cholestatic liver fibrosis

Lysyl oxidase-like 1 (LOXL1) proteins are amine oxidases that play a crucial role in extracellular matrix remodeling due to their collagen cross-linking and intracellular functions. The role of LOXL1 in cholestatic liver fibrosis remains unexplored. We measured LOXL1 expression in two murine models of cholestasis [Mdr2 knockout (Mdr2-/-) and bile duct ligation (BDL)]. We used adeno-associated virus (AAV) serotype 6-mediated hepatic delivery against LOXL1 (AAV2/6-shLoxl1) to investigate the therapeutic efficacy of targeting LOXL1 in cholestatic liver fibrosis. NIH-3T3 murine fibroblasts were used to investigate the function and regulatory mechanisms of LOXL1 in vitro. LOXL1 expression was significantly upregulated in Mdr2-/- and BDL mice compared with their corresponding controls, predominantly in collagen-rich fibrous septa and portal areas. AAV2/6-shLoxl1 significantly reduced LOXL1 levels in Mdr2-/- and BDL mice, mainly in desmin-positive hepatic stellate cells (HSCs) and fibroblasts. Concomitant with reduced LOXL1 expression, there was reduced ductular reaction, inflammation, and fibrosis in both Mdr2-/- and BDL mice. In addition, Loxl1 intervention decreased Ki-67-positive cells in the desmin-positive areas in both Mdr2-/- and BDL mice. Overexpression of LOXL1 significantly promoted fibroblast proliferation by activating the platelet-derived growth factor receptor and extracellular signal-regulated kinase signaling pathways in vitro. Our findings demonstrated that selective inhibition of LOXL1 derived from HSCs/fibroblasts attenuated cholestatic liver/biliary fibrosis, inflammation, ductal reaction, and HSC/fibroblast proliferation. Based on our findings, LOXL1 could be a potential therapeutic target for cholestatic fibrosis.NEW & NOTEWORTHY Selectively, inhibition of HSC/fibroblasts-derived LOXL1 by AAV2/6-shLoxl1 could reduce collagen deposition, HSC/fibroblasts proliferation, and cholestatic liver fibrosis progression. In addition, overexpression of LOXL1 significantly promoted HSC/fibroblast proliferation by activating the PDGFRß/PI3K and ERK signaling pathways in vitro.

The many faces and pathologic diagnostic challenges of autoimmune hepatitis

Autoimmune hepatitis (AIH) is an immune-mediated chronic inflammatory liver disease, characterized by hypergammaglobulinemia, the presence of specific autoantibodies, and typical abnormalities in liver histology. Prompt diagnosis and initiation of immunosuppressive treatment are necessary for both chronic and acute onset AIH to prevent progression to end-stage liver disease or fatal liver failure. However, the diagnosis of AIH is challenging mainly because of its heterogeneous clinical, serological and pathological features. Although portal lymphoplasmacytosis and interface hepatitis are the most typical histological features of AIH, many other histological features can be observed in AIH, including emperipolesis, hepatocyte rosettes, and Kupffer cell hyaline globules. Recent studies have questioned emperipolesis and hepatocyte rosette formation as typical features of AIH, and atypical clinical and histological presentations have also been recognized. This led an international working group to propose the modified AIH diagnostic criteria. However, it is well recognized that there are no pathognomonic characteristics that can be used to diagnose AIH and careful clinicopathological correlation is required to arrive at the correct diagnosis. The aim of this review is to summarize the histological features of AIH, its varied histopathologic spectrum, recent updates and major differential diagnoses in routine clinical practice.

Automated image analysis of keratin 7 staining can predict disease outcome in primary sclerosing cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease that obstructs the bile ducts and causes liver cirrhosis and cholangiocarcinoma. Efficient surrogate markers are required to measure disease progression. The cytokeratin 7 (K7) load in a liver specimen is an independent prognostic indicator that can be measured from digitalized slides using artificial intelligence (AI)-based models.

METHODS

A K7-AI model 2.0 was built to measure the hepatocellular K7 load area of the parenchyma, portal tracts, and biliary epithelium. K7-stained PSC liver biopsy specimens (n = 295) were analyzed. A compound endpoint (liver transplantation, liver-related death, and cholangiocarcinoma) was applied in Kaplan-Meier survival analysis to measure AUC values and positive likelihood ratios for each histological variable detected by the model.

RESULTS

The K7-AI model 2.0 was a better prognostic tool than plasma alkaline phosphatase, the fibrosis stage evaluated by Nakanuma classification, or K7 score evaluated by a pathologist based on the AUC values of measured variables. A combination of parameters, such as portal tract volume and area of K7-positive hepatocytes analyzed by the model, produced an AUC of 0.81 for predicting the compound endpoint. Portal tract volume measured by the model correlated with the histological fibrosis stage.

CONCLUSIONS

The K7 staining of histological liver specimens in PSC provides significant information on disease outcomes through objective and reproducible data, including variables that cannot be measured by a human pathologist. The K7-AI model 2.0 could serve as a prognostic tool for clinical endpoints and as a surrogate marker in drug trials.

In vitro expansion of cirrhosis derived liver epithelial cells with defined small molecules

BACKGROUND & AIMS

Mature hepatocytes have limited expansion capability in culture and rapidly loose key functions. Recently however, tissue culture conditions have been developed that permit rodent hepatocytes to proliferate and transform into progenitor-like cells with ductal characteristics in vitro. Analogous cells expressing both hepatic and duct markers can be found in human cirrhotic liver in vivo and may represent an expandable population.

METHODS

An in vitro culture system to expand epithelial cells from human end stage liver disease organs was developed by inhibiting the canonical TGF-β, Hedgehog and BMP pathways.

RESULTS

Human cirrhotic liver epithelial cells became highly proliferative in vitro. Both gene expression and DNA methylation site analyses revealed that cirrhosis derived epithelial liver cells were intermediate between normal hepatocytes and cholangiocytes. Mouse hepatocytes could be expanded under the same conditions and retained the ability to re-differentiate into hepatocytes upon transplantation. In contrast, human cirrhotic liver derived cells had only low re-differentiation capacity.

CONCLUSIONS

Epithelial cells of intermediate ductal-hepatocytic phenotype can be isolated from human cirrhotic livers and expanded in vitro. Unlike their murine counterparts they have limited liver repopulation potential.

Ultrastructural Profile Combined with Immunohistochemistry of a Hepatic Progenitor Cell Line in Pediatric Autoimmune Hepatitis: New Insights into the Morphological Pattern of the Disease

Considering that the heterogenic population of a hepatic progenitor cell line (HPCL) can play a vital role in autoimmune hepatitis (AIH), we decided to conduct pioneering retrospective evaluation of these cells in pediatric AIH by means of transmission electron microscopy (TEM). The aim of the study was to assess the ultrastructure of the HPCL in children with untreated AIH. Ultrastructural analysis of the HPCL population, preceded by immunohistochemical staining for cytokeratin 7 (CK7), was performed using pretreatment liver biopsies from 23 children with clinicopathologically diagnosed AIH. Immunohistochemical assessment for CK7 allowed detection of proliferating immature epithelial cells differentiating towards periportal and intralobular intermediate hepatocytes without marked formation of ductular reactions in AIH children. Using TEM, we distinguished three morphological types of HPCs: I—the most undifferentiated progenitor cells; III—intermediate hepatocyte-like cells; II—intermediate bile duct cells. Most frequent were the cells differentiating towards hepatocytes, most rare—those differentiating towards cholangiocytes. The results indicate that an HPCL may be an important source of hepatocyte regeneration. Ultrastructural analyses of the HPCL population, combined with immunohistochemistry for CK7, might be a useful tool to evaluate liver cell regeneration, including fibrogenesis, and may help better understand the morphological pattern of the disease, in pediatric AIH. Frequent appearance of an HPCL in the vicinity of fibrotic foci, often accompanied by hyperactive Kupffer cells and transitional hepatic stellate cells, may indicate their significant involvement in liver fibrogenesis.

Autoimmune biliary diseases: primary biliary cholangitis and primary sclerosing cholangitis

Autoimmune cholestatic liver diseases are rare hepato-biliary disorders characterized by a progressive, inflammatory destruction of bile ducts. Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are the main autoimmune cholestatic liver diseases. Both may evolve into secondary biliary cirrhosis and its complications. Therapeutic options are limited and liver transplantation remains the only definitive treatment for PBC and PSC.

Most PBC and PSC patients have a typical presentation, which does not require liver biopsy. However, in routine clinical practice, important variants or specific subgroups that benefit from liver biopsy for proper management may be observed. Herein, we provide a general overview of clinical and pathological characteristic of PBC and PSC, highlighting the most important features for routine diagnostic practice.

Pathology of autoimmune hepatitis

Autoimmune hepatitis (AIH) is a relatively rare non-resolving chronic liver disease, which mainly affects women. It is characterized by hypergammaglobulinemia, circulating autoantibodies, interface hepatitis on liver histology and a favourable response to immunosuppression. The putative mechanism for the development of autoimmune hepatitis is thought to be the interaction between genetic predisposition, environmental triggers and failure of the native immune system.

AIH still remains a major diagnostic and therapeutic challenge, mainly because it is a very heterogeneous disease. Prompt and timely diagnosis is crucial since, if left untreated, AIH has a high mortality rate. Histological demonstration of hepatitis is required for the diagnosis of AIH and, therefore, liver biopsy is mandatory in the initial diagnostic work-up, before treatment. In this review, we summarize the histological features of AIH with the main aim of highlighting the most important clinical-pathological hallmarks useful in the routine diagnostic practice.

Biliary damage and liver fibrosis are ameliorated in a novel mouse model lacking l-histidine decarboxylase/histamine signaling

Primary sclerosing cholangitis (PSC) is characterized by biliary damage and fibrosis. Multidrug resistance-2 gene knockout (Mdr2^-/-) mice and PSC patients have increased histamine (HA) levels (synthesized by l-histidine decarboxylase, HDC) and HA receptor (HR) expression. Cholestatic HDC^-/- mice display ameliorated biliary damage and hepatic fibrosis. The current study evaluated the effects of knockout of HDC^-/- in Mdr2^-/- mice (DKO) on biliary damage and hepatic fibrosis. WT, Mdr2^-/- mice, and homozygous DKO mice were used. Selected DKO mice were treated with HA. We evaluated liver damage along with HDC expression and HA serum levels. Changes in ductular reaction were evaluated along with liver fibrosis, inflammation and bile acid signaling pathways. The expression of H1HR/PKC-α/TGF-β1 and H2HR/pERK/VEGF-C was determined. In vitro, cholangiocyte lines were treated with HA with/without H1/H2 inhibitors before measuring: H1/H2HR, TGF-β1, and VEGF-C expression. Knockout of HDC ameliorates hepatic damage, ductular reaction, fibrosis, inflammation, bile acid signaling and H1HR/PKC-α/TGF-β1 and H2HR/pERK/VEGF-C signaling. Reactivation of the HDC/HA axis increased these parameters. In vitro, stimulation with HA increased HR expression and PKC-α, TGF-β1, and VEGF-C expression, which was reduced with HR inhibitors. Our data demonstrate the key role for the HDC/HA axis in the management of PSC progression.

The landscape of hepatobiliary adverse reactions across 53 herbal and dietary supplements reveals immune-mediated injury as a common cause of hepatitis

Recent evidence suggests herbal-induced liver injury (HILI) to account for 20% of cases among the U.S. Drug-Induced-Liver-Injury-Network. To define injury patterns of HILI, we reviewed the clinical data of 413 patients exposed to 53 HDS products by considering the evidence for HILI and its grades of severity. Outstandingly, females developed HILI more rapidly (p = 0.018) and the time to recovery was significantly increased (p = 0.0153). > 90% of reported cases were severe and half of HDS products caused acute liver failure (ALF) requiring liver transplantation or resulted in fatal outcomes. Liver biopsies of 243 patients defined 13 histological features; two-thirds of products elicited immune-mediated hepatitis and included 154 Hy's law positive cases. The histological injury patterns were confirmed among unrelated patients, while accidental re-challenges evidenced culprits as causative. Furthermore, one-fifth of patients presented elevated autoantibody titres indicative of autoimmune-like HILI, and one-third of the products were linked to chronic hepatitis and cholestatic injuries not resolving within 6 months. Lastly, INR and TBL are critical laboratory parameters to predict progression of severe HILI to ALF. Our study highlights the need for a regulatory framework to minimize the risk for HILI. Better education of the public and a physician-supervised self-medication plan will be important measures to abate risk of HILI.

Biliary features in liver histology of children with autoimmune liver disease

OBJECTIVES AND STUDY

Various degrees of biliary changes are considered to be part of the histological picture of children with pediatrics autoimmune liver disease (AILD), but the literature is scarce and confusing. We aimed to describe the characteristics of children with AILD (autoimmune hepatitis, AIH, and autoimmune sclerosing cholangitis, ASC) focusing on the prevalence and type of biliary abnormalities on initial biopsy to see whether ASC was predictable on histological ground.

METHODS

The files of children diagnosed with AILD were reviewed. The Ishak score was used to grade inflammation and fibrosis on biopsy; a biliary score was built to grade bile duct injury. Demographic, laboratory and histological features at diagnosis were reported and compared between the two groups (AIH vs ASC).

RESULTS

Forty-one patients were diagnosed with AIH (n = 24), ASC (n = 13) and PSC (n = 4) between 2009 and 2018. Twenty-nine patients [F = 76%, AIH = 20, ASC = 9, median age at diagnosis 11.7 (range 2.2-17.8)] were included in the study; 12 (4 with PSC) were excluded. Prevalence of inflammatory bowel disease was higher in ASC group (56% vs 10% in AIH, p < 0.05). On histology 17% had cirrhosis. The grade of biliopathy with AILD was moderate in 72% and severe in 31%, and overall more prominent in ASC (p = 0.031). The inflammation of the bile ducts was classified as "multifocal" or "diffuse" mainly in ASC patients (89% vs 45% in AIH, p = 0.043). Periductular fibrosis was reported in 52% of AILD patients, with a higher mean score in ASC group (p < 0.05). However, ductular reaction, biliary metaplasia and granulomatous cholangitis were equally reported in AIH and ASC, providing no clear-cut for the distinction of the two entities in the global histological evaluation.

CONCLUSIONS

Majority of patients with pediatrics AILD have "moderate" or "severe" features of biliopathy; AIH and ASC are not easily distinguishable on histological ground at diagnosis, and therefore, the cholangiogram remains the only effective tool to differentiate patients with AIH from those with ASC. Further prospective studies are needed to better define histological biliary features in AILD, assess if the biliopathy responds to immunosuppressive treatment and evaluate its impact on long-term outcome.

AICAR-Induced AMPK Activation Inhibits the Noncanonical NF-κB Pathway to Attenuate Liver Injury and Fibrosis in BDL Rats

BACKGROUND

To evaluate the AMP-activated protein kinase- (AMPK-) mediated signaling and NF-κB-related inflammatory pathways that contribute to cholestatic diseases in the bile duct ligation (BDL) rat model of chronic cholestasis and verify the protective role of 5-Aminoimidazole-4-carboxamide1-β-D-ribofuranoside (AICAR) against hepatic injury and fibrosis triggered by cholestasis-related inflammation.

METHODS

Animals were randomly divided into three groups: sham-operated group, BDL group, and BDL+ AICAR group. Cholestatic liver injury was induced by common BDL. Two weeks later, rats in BDL+AICAR group started receiving AICAR treatment. Hepatic pathology was examined by haematoxylin and eosin (H&E) and sirius red staining and hydroxyproline assay was performed in evaluating the severity of hepatic cirrhosis. Real-time PCR and Western blot were performed for RNA gene expression of RNA and protein levels, respectively.

RESULTS

The BDL group showed liver injury as evidenced by histological changes and elevation in serum biochemicals, ductular reaction, fibrosis, and inflammation. The mRNA expression of canonical NF-κB inflammatory cytokines such as TNF-α, IL-1β, TGF-β, and the protein of noncanonical NF-κB, P100, and P52 was upregulated in the livers of BDL rats. The BDL rats with the administration of AICAR could induce AMPK activation inhibiting the noncanonical NF-κB pathway to attenuate liver injury and fibrosis in BDL rats.

CONCLUSION

The BDL model of hepatic cholestatic injury resulting in activation of Kupffer cells and recruitment of immune cells might initiate an inflammatory response through activation of the NF-κB pathway. The AMPK activator AICAR significantly alleviated BDL-induced inflammation in rats by mainly inhibiting the noncanonical NF-κB pathway and thus protecting against hepatic injury and fibrosis triggered by BDL.

Overlap Syndrome of Autoimmune Hepatitis and Primary Biliary Cholangitis

Overlap syndrome of autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) is typically defined as concomitant or serial presentation with clinical features of both of these 2 distinct diseases. The Paris criteria and variations of the International Autoimmune Hepatitis group scoring systems for the diagnosis of AIH have been used to diagnose overlap syndrome. If left untreated, patients with overlap syndrome will have higher rates of portal hypertension, gastrointestinal bleeding, ascites, death, and need for liver transplant. Therefore, early identification is essential in providing appropriate therapy to potentially prevent long-term adverse outcomes in patients with overlap syndrome.

Direct Conversion of Mouse Fibroblasts into Cholangiocyte Progenitor Cells

Disorders of the biliary epithelium, known as cholangiopathies, cause severe and irreversible liver diseases. The limited accessibility of bile duct precludes modeling of several cholangiocyte-mediated diseases. Therefore, novel approaches for obtaining functional cholangiocytes with high purity are needed. Previous work has shown that the combination of Hnf1β and Foxa3 could directly convert mouse fibroblasts into bipotential hepatic stem cell-like cells, termed iHepSCs. However, the efficiency of converting fibroblasts into iHepSCs is low, and these iHepSCs exhibit extremely low differentiation potential into cholangiocytes, thus hindering the translation of iHepSCs to the clinic. Here, we describe that the expression of Hnf1α and Foxa3 dramatically facilitates the robust generation of iHepSCs. Notably, prolonged in vitro culture of Hnf1α- and Foxa3-derived iHepSCs induces a Notch signaling-mediated secondary conversion into cholangiocyte progenitor-like cells that display dramatically enhanced differentiation capacity into mature cholangiocytes. Our study provides a robust two-step approach for obtaining cholangiocyte progenitor-like cells using defined factors.

Autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe liver disease that affects children and adults worldwide. The diagnosis of AIH relies on increased serum transaminase and immunoglobulin G levels, presence of autoantibodies and interface hepatitis on liver histology. AIH arises in genetically predisposed individuals when a trigger, such as exposure to a virus, leads to a T cell-mediated autoimmune response directed against liver autoantigens; this immune response is permitted by inadequate regulatory immune control leading to a loss of tolerance. AIH responds favourably to immunosuppressive treatment, which should be started as soon as the diagnosis is made. Standard regimens include fairly high initial doses of corticosteroids (prednisone or prednisolone), which are tapered gradually as azathioprine is introduced. For those patients who do not respond to standard treatment, second-line drugs should be considered, including mycophenolate mofetil, calcineurin inhibitors, mechanistic target of rapamycin (mTOR) inhibitors and biologic agents, which should be administered only in specialized hepatology centres. Liver transplantation is a life-saving option for those who progress to end-stage liver disease, although AIH can recur or develop de novo after transplantation. In-depth investigation of immune pathways and analysis of changes to the intestinal microbiota should advance our knowledge of the pathogenesis of AIH and lead to novel, tailored and better tolerated therapies.

Autoimmune hepatitis: current challenges and future prospects

Autoimmune hepatitis (AIH) is a chronic progressive liver disease characterized by high levels of aminotransferases and autoantibodies, hypergammaglobulinemia, and interface hepatitis. AIH affects all races and all ages worldwide, regardless of sex, although a preponderance of females is a constant finding. The etiology of AIH has not been completely elucidated, but immunogenetic background and environmental parameters may contribute to its development. The most important genetic factor is human leukocyte antigens (HLAs), especially HLA-DR, whereas the role of environmental factors is not completely understood. Immunologically, disruption of the immune tolerance to autologous liver antigens may be a trigger of AIH. The diagnosis of classical AIH is fairly easy, though not without pitfalls. In contrast, the diagnosis of atypical AIH poses great challenges. There is confusion as to the definition of the disease entity and its boundaries in the diagnosis of overlap syndrome, drug-induced autoimmune hepatitis, and AIH with concomitant nonalcoholic fatty liver disease (NAFLD) or chronic hepatitis C. Centrilobular zonal necrosis is now included in the histological spectrum of AIH. However, the definition and the significance of AIH presenting with centrilobular zonal necrosis have not been examined extensively. In ~20% of AIH patients who are treated for the first time with standard therapy, remission is not achieved. The development of more effective and better tolerated novel therapies is an urgent need. In this review, we discuss the current challenges and the future prospects in relation to the diagnosis and treatment of AIH, which have been attracting considerable recent attention.