Different HLA class II associations in ulcerative colitis patients with and without primary sclerosing cholangitis

Novel Genetic Risk Variants and Clinical Predictors Associated With Primary Sclerosing Cholangitis in Patients With Ulcerative Colitis

INTRODUCTION

Patients with ulcerative colitis (UC) who are likely to have primary sclerosing cholangitis (PSC) should be identified because PSC can influence UC clinical behavior and outcomes.The aim of this study was to establish a model incorporating clinical and genetic risk predictors that identifies patients with UC at risk of developing PSC.

METHODS

We conducted a retrospective case-control study. Inflammatory bowel disease cohorts from multiple institutions were used as discovery and replicate datasets. Quality control criteria, including minor allele frequency, call rates, Hardy-Weinberg equilibrium, cryptic relatedness, and population stratification (through principal components), were used. Discriminative accuracy was evaluated with area under the receiver operating characteristic curve.

RESULTS

Fifty-seven of 581 patients (9.8%) with UC had PSC. Multivariate analysis showed that patients with UC-PSC had more extensive disease (odds ratio [OR], 5.42; P = 1.57E-04), younger diagnosis age (younger than 20 years; OR, 2.22; P = 0.02), and less smoking (OR, 0.42; P = 0.02) than those with UC. After linkage disequilibrium pruning and multivariate analyses, 3 SNPs (rs3131621 at 6p21.33; rs9275596 and rs11244 at 6p21.32) at the HLA region were found associated with a 2- to 3-fold increased risk of PSC. Our model demonstrated good discriminatory power (area under the receiver operating characteristic curve, 88%).

DISCUSSION

Three variants in HLA (6p21.3) region significantly distinguished patients with UC-PSC from patients with UC alone. Once further validated in an independent large cohort, our model could be used to identify patients with UC at risk of PSC, and it could also help guide disease management.

Recent Insights into Pediatric Primary Sclerosing Cholangitis

This article reviews recent literature on the pathogenesis, presentation, diagnosis, comorbidities, natural history, and management of pediatric primary sclerosing cholangitis (PSC). The authors shed light on the role of genetic and environmental factors in PSC, although recognize the limitations in the understanding of PSC pathogenesis. They reflect on presenting disease phenotypes, including the association with inflammatory bowel disease and frequent histologic presence of autoimmune hepatitis features. The current lack of effective medications is discussed, and disease complications and prognosis are described. Finally, the authors highlight available evidence while acknowledging the paucity of prospective pediatric data.

Cutting edge issues in juvenile sclerosing cholangitis

Sclerosing cholangitis (SC) is a rare chronic disorder characterised by inflammation and progressive obliterative fibrosis of the intrahepatic and/or extrahepatic bile ducts. Diagnosis is based on cholangiogram showing bile duct dilatation, narrowing and obliteration of the biliary tree, and histologically, on the presence of inflammatory bile duct damage leading to periductal fibrosis. In children the most common SC is associated with strong autoimmune features, overlapping with those of autoimmune hepatitis (AIH); this form is known as autoimmune sclerosing cholangitis, ASC. Conversely, primary SC (PSC), a condition in which the term "primary" indicates that aetiology and pathogenesis are unknown, is rare in paediatrics. Secondary SC (SSC) defines a cholangiopathy associated with an identifiable aetiology such as immunodeficiencies, infections or haematological disorders. ASC and PSC are strongly associated with inflammatory bowel disease (IBD). ASC responds biochemically well to immunosuppressive drugs and ursodeoxycholic acid (UDCA). Primary forms are exclusively managed with oral UDCA, while in the secondary forms the medical treatment depends on the underlying aetiology. Despite treatment, SC often progresses to biliary cirrhosis and end-stage liver disease requiring liver transplantation. The disease can recur after transplant. Better understanding of pathogenic mechanisms and better treatment modalities are needed to improve the prognosis of this invalidating hepatic disorder.

Distinct Disease Phenotype of Ulcerative Colitis in Patients With Coincident Primary Sclerosing Cholangitis: Evidence From a Large Retrospective Study With Matched Cohorts

BACKGROUND

Primary sclerosing cholangitis is a classical extraintestinal manifestation in patients with ulcerative colitis. However, the impact of primary sclerosing cholangitis on the disease course is incompletely understood.

OBJECTIVE

This study aimed to assess the impact of primary sclerosing cholangitis on disease phenotype and its course in patients with ulcerative colitis.

DESIGN

This is a retrospective study with 3:1 matched cohorts.

SETTINGS

Tertiary care center's electronic database was used for data analysis from 2000 and 2018.

PATIENTS

Of 782 patients with ulcerative colitis, 77 patients who had coincident primary sclerosing cholangitis were included.

MAIN OUTCOME MEASURES

The primary outcomes evaluated were disease characteristics including colonic disease activity, temporal change of disease course, colorectal neoplasia, and colectomy rates.

RESULTS

Disease activity during acute flares, assessed by the complete Mayo score, was significantly lower in patients with primary sclerosing cholangitis (6.2 vs 7.3; p < 0.001). In addition, disease activity in patients with primary sclerosing cholangitis was decreased, especially within the first 10 years after disease onset, and biological therapy with anti-tumor necrosis factor and anti-integrin agents was commenced less frequently (22% vs 35%; p = 0.043) and later (10-year risk: 17.4% vs 27.8%; p = 0.034). Patients with primary sclerosing cholangitis were younger at colitis diagnosis (23.3 vs 29.3 years; p < 0.001) and had more extensive disease (75% vs 46%; p < 0.001). Colorectal cancer was more frequently detected in patients with coincident primary sclerosing cholangitis (6/77 vs 16/705; p = 0.016). Colectomy rates did not differ between both groups (14.3% vs 14.5%; p = 0.56). In contrast, patients with ulcerative colitis had to undergo surgery more frequently because of therapy-refractant inflammation, whereas surgery due to neoplasia development was increased in patients with coincident primary sclerosing cholangitis (p = 0.013).

LIMITATIONS

The study was limited by its retrospective design.

CONCLUSION

Patients who have ulcerative colitis with coincident primary sclerosing cholangitis develop a distinct disease course characterized by an earlier disease onset and lower disease activity, but more frequent extensive disease manifestation and higher risk for colorectal cancer. See Video Abstract at http://links.lww.com/DCR/B45. FENOTIPO DE ENFERMEDAD DISTINTIVO DE LA COLITIS ULCERATIVA EN PACIENTES CON COLANGITIS ESCLEROSANTE PRIMARIA CONCOMITANTE: EVIDENCIA DE UN ESTUDIO RETROSPECTIVO GRANDE CON COHORTES EMPAREJADAS: La colangitis esclerosante primaria es una manifestación extraintestinal clásica en pacientes con colitis ulcerativa. Sin embargo, el impacto de la colangitis esclerosante primaria en el curso de la enfermedad no es comprendido completamente.Evaluar el impacto de la colangitis esclerosante primaria en el fenotipo y curso de la enfermedad en pacientes con colitis ulcerativa.Este es un estudio retrospectivo con cohortes emparejadas 3:1.La base de datos electrónica de un centro de atención terciaria se utilizó para el análisis de datos de 2000 a 2018.782 pacientes con colitis ulcerativa, 77 padecían colangitis esclerosante primaria concomitante y fueron incluidos.Se evaluaron las características de la enfermedad, incluida la actividad de enfermedad colónica, el cambio temporal del curso de la enfermedad, la neoplasia colorrectal y las tasas de colectomía.La actividad de la enfermedad durante los brotes agudos, evaluada por la puntuación completa de Mayo, fue significativamente menor en pacientes con colangitis esclerosante primaria (6.2 vs 7.3; p < 0.001). Además, la actividad de la enfermedad en pacientes con colangitis esclerosante primaria se redujo especialmente en los primeros 10 años después del inicio de la enfermedad, y la terapia biológica con agentes anti-TNF y anti-integrina se inició con menos frecuencia (22% vs 35%; p = 0.043) y más tarde (riesgo a 10 años: 17.4% vs 27.8%; p = 0.034). Los pacientes con colangitis esclerosante primaria eran más jóvenes en el momento del diagnóstico de colitis (23.3 vs 29.3 años; p < 0.001) y tenían enfermedad más extensa (75% vs 46%; p < 0.001). El cáncer colorrectal se detectó con mayor frecuencia en pacientes con colangitis esclerosante primaria concomitante (6/77 vs 16/705; p = 0.016). Las tasas de colectomía no fueron diferentes entre ambos grupos (14.3% vs 14.5%; p = 0.56). En contraste, los pacientes con colitis ulcerativa tuvieron que someterse a cirugía con mayor frecuencia debido a inflamación refractaria a la terapia, mientras que el desarrollo de neoplasia se incrementó en pacientes con colangitis esclerosante primaria concomitante (p = 0.013).El estudio estuvo limitado por su diseño retrospectivo.Los pacientes con colitis ulcerativa con colangitis esclerosante primaria concomitante desarrollan un curso de enfermedad distintivo caracterizado por un inicio temprano de la enfermedad y una menor actividad de la enfermedad, pero con manifestación de enfermedad extensa más frecuente y un mayor riesgo de cáncer colorrectal. Vea el resumen en video en http://links.lww.com/DCR/B45.

Review article: the genetics of the human leucocyte antigen region in inflammatory bowel disease

BACKGROUND

The human leucocyte antigen (HLA) complex, located at chromosome 6p21.3 is a highly polymorphic region containing the classical class I and II HLA genes. The region is highly associated with inflammatory bowel disease (IBD), largely through genome-wide association studies (GWAS).

AIMS

To review the role of HLA in immune function, summarise data on risk/protective HLA genotypes for IBD, discuss the role of HLA in IBD pathogenesis, treatment and examine limitations that might be addressed by future research.

METHODS

An organised search strategy was used to collate articles describing HLA genes in IBD, including Crohn's disease and ulcerative colitis.

RESULTS

All classical HLA genes with variation (including HLA-A, B, C, DRB1, DQA1, DQB1, DPA1 and DPB1) harbour IBD-associated genotypes. The most implicated gene is HLA-DRB1, with HLA-DRB1*03:01 the most associated risk allele in both Crohn's disease and ulcerative colitis. Elucidating precise disease associations is challenging due to high linkage disequilibrium between HLA genotypes. The mechanisms by which risk alleles cause disease are multifactorial, with the best evidence indicating structural and electrostatic alteration impacting antigen binding and downstream signalling. Adverse medication events have been associated with HLA genotypes including with thiopurines (pancreatitis) and anti-TNF agents (antibody formation).

CONCLUSIONS

The HLA complex is associated with multiple risk/protective alleles for IBD. Future research utilising long-read technology, ascertainment of zygosity and integration in disease modelling will improve the functional understanding and clinical translation of genetic findings.

Clinical profile and outcome of primary sclerosing cholangitis: A single-centre experience from western India

INTRODUCTION

Primary sclerosing cholangitis (PSC), a chronic progressive cholestatic liver disease of unknown cause, is uncommon in India. The aim of this study was to define the profile and outcomes of patients with PSC in a tertiary centre from western India.

METHODS

A retrospective study of the prospectively maintained liver clinic database was searched for cases of PSC between January 2008 and December 2017 with minimum 6 months follow up. All cases were reviewed for clinical profile, inflammatory bowel disease (IBD) co-morbidity and major endpoints like death, cholangiocarcinoma and liver transplantation (LT).

RESULTS

We identified 28 (18 men) patients with PSC (19, 67% large-duct and 9, 33% small-duct) with a median age of 31.5 years (range 7-63 years) with median duration of follow up of 24 months (6-125 months). Six (21.4%) had autoimmune hepatitis (AIH-PSC) overlap. Inflammatory bowel disease was seen in 12 (43%) cases, all were ulcerative colitis (UC). During follow up, seven patients (25%) developed dominant stricture or recurrent cholangitis, 11 (39%) had  portal hypertension, 2 (7%) developed cholangiocarcinoma and 5 (17.8%) progressed to hepatic  decompensation on follow up. Ten (35%) patients died, 5 from liver-related complications, 2 from cholangiocarcinoma, 1 each from brain hemorrhage and systemic sepsis and 1 due to unknown cause; 3 underwent liver transplantation. Revised Mayo score of patients who survived was lower than those who died (1.03 vs. 1.86, p value 0.03).

CONCLUSION

PSC commonly presents in young age and rapidly progresses to decompensation. Prevalence of IBD in PSC is lower and the proportion of small-duct PSC is higher than that observed in western populations.

Specific Features of Patients With Inflammatory Bowel Disease and Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is a chronic and progressive disease of the biliary tract. PSC is strongly associated with inflammatory bowel disease (IBD), mainly with ulcerative colitis, and most PSC patients have underlying IBD. The pathophysiological interactions between IBD and PSC are unclear, although it seems that the patients with IBD and PSC have a distinct phenotype. IBD with coexisting PSC is more extensive and is characterized by milder activity compared to IBD alone. The coexistence of PSC increases the risk for colorectal cancer in IBD patients and lifelong annual surveillance colonoscopy is recommended. Also, liver transplantation (LT) for PSC may affect the course of IBD. In addition, the management of IBD after LT includes many specific problems. On the other hand, the effect of IBD on the natural history of PSC appears to be milder. However, IBD may increase the risk of postsurgical complications after LT and is a risk factor for recurrent PSC after LT. Overall, the coexistence of IBD with PSC changes the management, natural history and prognosis of both diseases.

Autoimmune liver diseases and inflammatory bowel diseases in children: current issues and future perspectives

Inflammatory bowel diseases (IBDs) represent a group of intestinal disorders with a chronic and relapsing inflammation of the gut, and with a potential risk of systemic involvement of other organs and systems. Over the pediatric age, an incidence higher than 20% of developing extraintestinal manifestation during follow-up has been reported. The liver and the biliary system are frequently involved, and primary sclerosing cholangitis (PSC) is the most predominant entity with an incidence rate of 6.4-7.8% in children. PSC recognizes a multifactorial pathogenesis, and so far a not fully known mechanism for this association. The peculiar phenotype and the distinct clinical course of patients with IBD and PSC-associated make this 'linkage' an attractive study model to better understand mechanisms underlying these diseases. Approaching to these patients is complex and multidisciplinary, and a unique therapeutic strategy has not been standardized yet. New medications are being studied; however, further studies are needed to fully understand the pathogenesis and to improve the care of these patients. The aim of this paper is to review the recent literature regarding hepatobiliary involvement in IBD patients, with particular attention to PSC, and to provide the latest information for a correct diagnosis and appropriate management.

Interactions between primary sclerosing cholangitis and inflammatory bowel disease: implications in the adult liver transplant setting

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease which is associated with inflammatory bowel disease (IBD) in most cases. As there is currently no medical therapy which alters the natural history of PSC, liver transplantation may be required. Areas covered: We searched for articles in PubMed and critically reviewed current literature on the interrelationship between PSC and IBD with a specific focus on considerations for patients in the liver transplant setting. Expert commentary: PSC is an uncommon disease which limits available studies to be either retrospective or contain relatively small numbers of patients. Based on observations from these studies, the behavior and complications of PSC and IBD impact on each other both before and after a liver transplant. Both these autoimmune conditions and their associated cancer risk also influence patient selection for transplantation and may be impacted by immunosuppression use post-transplant. Hence, a complex interplay exists between PSC, IBD and liver transplantation which requires clarification with ongoing research.

HLA haplotypes in primary sclerosing cholangitis patients of admixed and non-European ancestry

Primary sclerosing cholangitis (PSC) is strongly associated with several human leukocyte antigen (HLA) haplotypes. Due to extensive linkage disequilibrium and multiple polymorphic candidate genes in the HLA complex, identifying the alleles responsible for these associations has proven difficult. We aimed to evaluate whether studying populations of admixed or non-European descent could help in defining the causative HLA alleles. When assessing haplotypes carrying HLA-DRB1*13:01 (hypothesized to specifically increase the susceptibility to chronic cholangitis), we observed that every haplotype in the Scandinavian PSC population carried HLA-DQB1*06:03. In contrast, only 65% of HLA-DRB1*13:01 haplotypes in an admixed/non-European PSC population carried this allele, suggesting that further assessments of the PSC-associated haplotype HLA-DRB1*13:01-DQA1*01:03-DQB1*06:03 in admixed or multi-ethnic populations could aid in identifying the causative allele.

Genetics of primary sclerosing cholangitis and pathophysiological implications

Primary sclerosing cholangitis (PSC) is a chronic disease leading to fibrotic scarring of the intrahepatic and extrahepatic bile ducts, causing considerable morbidity and mortality via the development of cholestatic liver cirrhosis, concurrent IBD and a high risk of bile duct cancer. Expectations have been high that genetic studies would determine key factors in PSC pathogenesis to support the development of effective medical therapies. Through the application of genome-wide association studies, a large number of disease susceptibility genes have been identified. The overall genetic architecture of PSC shares features with both autoimmune diseases and IBD. Strong human leukocyte antigen gene associations, along with several susceptibility genes that are critically involved in T-cell function, support the involvement of adaptive immune responses in disease pathogenesis, and position PSC as an autoimmune disease. In this Review, we survey the developments that have led to these gene discoveries. We also elaborate relevant interpretations of individual gene findings in the context of established disease models in PSC, and propose relevant translational research efforts to pursue novel insights.

Antineutrophil antibodies define clinical and genetic subgroups in primary sclerosing cholangitis

BACKGROUND & AIMS

The strongest genetic risk factors in primary sclerosing cholangitis (PSC) are encoded in the HLA complex. Antineutrophil cytoplasmic antibodies (ANCA) have been reported in up to 94% of PSC patients, but their clinical significance and immunogenetic basis are ill defined. We aimed to characterize clinical and genetic associations of ANCA in PSC.

METHODS

Antineutrophil cytoplasmic antibodies were analysed with indirect immunofluorescence in 241 Norwegian PSC patients. HLA-B and HLA-DRB1 genotyping was performed in the patients and in 368 healthy controls. Data on perinuclear ANCA (pANCA) and HLA-DRB1 were available from 274 ulcerative colitis (UC) patients without known liver disease.

RESULTS

Antineutrophil cytoplasmic antibodies were found in 193 (80%) of the PSC patients, with pANCA in 169 (70%). ANCA-positive patients were younger than ANCA negative at diagnosis of PSC and had a lower frequency of biliary cancer (9% vs 19%, P=.047). There were no differences between PSC patients with and without inflammatory bowel disease. Genetically, the strong PSC risk factors HLA-B*08 (frequency in healthy 13%) and DRB1*03 (14%) were more prevalent in ANCA-positive than -negative patients (43% vs 25%, P=.0012 and 43% vs 25%, P=.0015 respectively). The results were similar when restricting the analysis to pANCA-positive patients. In UC patients without liver disease, HLA-DRB1*03 was more prevalent in pANCA-positive compared with -negative patients (P=.03).

CONCLUSIONS

Antineutrophil cytoplasmic antibodies identified PSC patients with particular clinical and genetic characteristics, suggesting that ANCA may mark a clinically relevant pathogenetic subgroup in the PSC-UC disease spectrum.

HLA class II alleles in Norwegian patients with coexisting type 1 diabetes and celiac disease

BACKGROUND

Type 1 diabetes (T1D) and celiac disease (CeD) are 2 distinct diseases, but there is an increased risk of developing CeD for T1D patients. Both diseases are associated with HLA-class II alleles, such as DQB1 *02:01 and DQB1 *03:02; however, their risk contribution vary between the diseases.

MATERIALS AND METHODS

We genotyped HLA-DRB1 and - DQB1 in 215 patients with coexisting T1D and CeD identified from a T1D cohort, and compared them to patients with T1D (N = 487) and CeD (N = 327), as well as healthy controls (N = 368).

RESULTS

The patients with coexisting T1D and CeD had an intermediate carrier frequency (72.8%) of the DRB1 *03:01- DQB1 *02:01- DQA1 *05:01 haplotype compared to T1D (64.1%) and CeD (88.7%) patients. The DRB1 *03:01- DQB1 *02:01- DQA1 *05:01/ DRB1 *04- DQB1 *03:02- DQA1 *03 haplotype combination, encoding DQ2.5 and DQ8 molecules, was equally frequent among patients with both T1D and CeD (52.6%) and T1D patients (46.8%) but significantly lower in CeD patients (9.5%).

CONCLUSION

Overall, the patients with coexisting T1D and CeD had an HLA profile more similar to T1D patients than CeD patients.

Sclerosing Cholangitis in Children and Adolescents

Sclerosing cholangitis in pediatric age is a severe disease, often associated with inflammatory bowel disease. It recognizes different etiologies. Management and prognosis depend on the underlying cause. A high proportion of patients have autoimmune features similar to those of autoimmune hepatitis and respond biochemically to immunosuppression, although bile duct disease progresses in half of them leading to liver transplant. The disease can recur after transplant. Severity of liver disease and risk of recurrence after transplant are linked to the severity of bowel disease.

Primary Sclerosing Cholangitis: Multiple Phenotypes, Multiple Approaches

Primary sclerosing cholangitis (PSC) is a heterogeneous, idiopathic, inflammatory disorder frequently associated with inflammatory bowel diseases. PSC patients may be classified into several subphenotypes. Investigations of pediatric, nonwhite, and female PSC patients have revealed distinguishing features. The natural history of PSC is variable in progression with numerous possible clinical outcomes. PSC patients may suffer bacterial cholangitis, cholangiocarcinoma, or colorectal adenocarcinoma. Treatments focusing on bile acid therapy and immunosuppression have not proven beneficial. Interest in PSC and international collaboration has led to improved understanding of the heterogeneity and the genetic structure and introduced possible effective therapeutics.

Using GWAS to identify genetic predisposition in hepatic autoimmunity

Primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) represent the three major hepatic autoimmune conditions. Patient morbidity and mortality remain high across these three diseases, and an unmet need for rational therapy exists. Disease understanding has focused on combining clinical and laboratory based science to provide better insights into the joint host and environmental factors necessary for the initiation, and perpetuation, of hepato-biliary inflammation. Twin studies, family studies, population studies and an inter-relationship with other autoimmune phenomena suggest a genetic component to risk for each disease. Until recently, understanding of this genetic risk has been limited to HLA haplotypes. Associations with risk-conferring and protective HLA haplotypes are present in all three diseases. Over the last few years, genome-wide association studies (GWAS), and related genetic association studies, have greatly increased understanding of the genetic risk signature of these three diseases and autoimmunity in general. Here we consider the rationale for GWAS in general and with specific reference to hepatic autoimmunity. We consider the process of GWAS, and highlight major findings to date. Potential functional implications of key findings are discussed including the IL-12/STAT4 pathway in PBC and the CD28/IL-2 pathway in PSC. We describe the marked pleiotropy demonstrated by PBC and PSC, which is consistent with other autoimmune diseases. Further, we focus on specific gene associations including SH2B3, which is common to all three diseases, and FUT2 in PSC, which represents a link between environment and genetics. We review attempts to translate GWAS findings into basic laboratory models including in vivo systems and highlight where clinical observations relate to genetics. Finally we describe deficiencies in GWAS to date and consider future study of genetics in hepatic autoimmunity.

Association of HLA-DRB1 amino acid residues with giant cell arteritis: genetic association study, meta-analysis and geo-epidemiological investigation

INTRODUCTION

Giant cell arteritis (GCA) is an autoimmune disease commonest in Northern Europe and Scandinavia. Previous studies report various associations with HLA-DRB1*04 and HLA-DRB1*01; HLA-DRB1 alleles show a gradient in population prevalence within Europe. Our aims were (1) to determine which amino acid residues within HLA-DRB1 best explained HLA-DRB1 allele susceptibility and protective effects in GCA, seen in UK data combined in meta-analysis with previously published data, and (2) to determine whether the incidence of GCA in different countries is associated with the population prevalence of the HLA-DRB1 alleles that we identified in our meta-analysis.

METHODS

GCA patients from the UK GCA Consortium were genotyped by using single-strand oligonucleotide polymerization, allele-specific polymerase chain reaction, and direct sequencing. Meta-analysis was used to compare and combine our results with published data, and public databases were used to identify amino acid residues that may explain observed susceptibility/protective effects. Finally, we determined the relationship of HLA-DRB1*04 population carrier frequency and latitude to GCA incidence reported in different countries.

RESULTS

In our UK data (225 cases and 1378 controls), HLA-DRB1*04 carriage was associated with GCA susceptibility (odds ratio (OR) = 2.69, P = 1.5×10(-11)), but HLA-DRB1*01 was protective (adjusted OR = 0.55, P = 0.0046). In meta-analysis combined with 14 published studies (an additional 691 cases and 4038 controls), protective effects were seen from HLA-DR2, which comprises HLA-DRB1*15 and HLA-DRB1*16 (OR = 0.65, P = 8.2×10(-6)) and possibly from HLA-DRB1*01 (OR = 0.73, P = 0.037). GCA incidence (n = 17 countries) was associated with population HLA-DRB1*04 allele frequency (P = 0.008; adjusted R(2) = 0.51 on univariable analysis, adjusted R(2) = 0.62 after also including latitude); latitude also made an independent contribution.

CONCLUSIONS

We confirm that HLA-DRB1*04 is a GCA susceptibility allele. The susceptibility data are best explained by amino acid risk residues V, H, and H at positions 11, 13, and 33, contrary to previous suggestions of amino acids in the second hypervariable region. Worldwide, GCA incidence was independently associated both with population frequency of HLA-DRB1*04 and with latitude itself. We conclude that variation in population HLA-DRB1*04 frequency may partly explain variations in GCA incidence and that HLA-DRB1*04 may warrant investigation as a potential prognostic or predictive biomarker.

Primary sclerosing cholangitis - the Norwegian experience

Research related to primary sclerosing cholangitis (PSC) has since 1980 been a major activity at the Oslo University Hospital Rikshospitalet. The purpose of this publication is to describe the development of this research, the impact of this research on the clinical handling of the patients, and finally to describe what we believe are the most urgent, remaining problems to be solved. During the early years, our research dealt primarily with clinical aspects of the disease. The concomitant inflammatory bowel disease (IBD) seen in most patients with PSC was a major interest and we also started looking into genetic associations of PSC. Prognosis, malignancy development and treatment with special emphasis on transplantation have later been dealt with. These activities has had impact on several aspects of PSC management; when and how to diagnose PSC and variant forms of PSC, how to handle IBD in PSC and how to deal with the increased rate of malignancy? The problems remaining to be solved are many. What is the role of the gut and the gut microbiota in the development of PSC? Do the PSC patients have an underlying disturbance in the bile homeostasis? And how does the characteristic type of fibrosis in PSC develop? The genetic studies have supported a role for the adaptive immune system in the disease development, but how should this be dealt with? Importantly, the development of malignancy in PSC is still not understood, and we lack appropriate medical treatment for our patients.

Development of a high-resolution NGS-based HLA-typing and analysis pipeline

The human leukocyte antigen (HLA) complex contains the most polymorphic genes in the human genome. The classical HLA class I and II genes define the specificity of adaptive immune responses. Genetic variation at the HLA genes is associated with susceptibility to autoimmune and infectious diseases and plays a major role in transplantation medicine and immunology. Currently, the HLA genes are characterized using Sanger- or next-generation sequencing (NGS) of a limited amplicon repertoire or labeled oligonucleotides for allele-specific sequences. High-quality NGS-based methods are in proprietary use and not publicly available. Here, we introduce the first highly automated open-kit/open-source HLA-typing method for NGS. The method employs in-solution targeted capturing of the classical class I (HLA-A, HLA-B, HLA-C) and class II HLA genes (HLA-DRB1, HLA-DQA1, HLA-DQB1, HLA-DPA1, HLA-DPB1). The calling algorithm allows for highly confident allele-calling to three-field resolution (cDNA nucleotide variants). The method was validated on 357 commercially available DNA samples with known HLA alleles obtained by classical typing. Our results showed on average an accurate allele call rate of 0.99 in a fully automated manner, identifying also errors in the reference data. Finally, our method provides the flexibility to add further enrichment target regions.

Refinement of the MHC risk map in a scandinavian primary sclerosing cholangitis population

Background

Genetic variants within the major histocompatibility complex (MHC) represent the strongest genetic susceptibility factors for primary sclerosing cholangitis (PSC). Identifying the causal variants within this genetic complex represents a major challenge due to strong linkage disequilibrium and an overall high physical density of candidate variants. We aimed to refine the MHC association in a geographically restricted PSC patient panel.

Methodology/Principal Findings

A total of 365 PSC cases and 368 healthy controls of Scandinavian ancestry were included in the study. We incorporated data from HLA typing (HLA-A, -B, -C, -DRB3, -DRB1, -DQB1) and single nucleotide polymorphisms across the MHC (n = 18,644; genotyped and imputed) alongside previously suggested PSC risk determinants in the MHC, i.e. amino acid variation of DRβ, a MICA microsatellite polymorphism and HLA-C and HLA-B according to their ligand properties for killer immunoglobulin-like receptors. Breakdowns of the association signal by unconditional and conditional logistic regression analyses demarcated multiple PSC associated MHC haplotypes, and for eight of these classical HLA class I and II alleles represented the strongest association. A novel independent risk locus was detected near NOTCH4 in the HLA class III region, tagged by rs116212904 (odds ratio [95% confidence interval] = 2.32 [1.80, 3.00], P = 1.35×10⁻¹¹).

Conclusions/Significance

Our study shows that classical HLA class I and II alleles, predominantly at HLA-B and HLA-DRB1, are the main risk factors for PSC in the MHC. In addition, the present assessments demonstrated for the first time an association near NOTCH4 in the HLA class III region.

Small duct primary sclerosing cholangitis without inflammatory bowel disease is genetically different from large duct disease

BACKGROUND & AIMS

Small duct primary sclerosing cholangitis (PSC) is phenotypically a mild version of large duct PSC, but it is unknown whether these phenotypes share aetiology. We aimed to characterize their relationship by investigating genetic associations in the human leucocyte antigen (HLA) complex, which represent the strongest genetic risk factors in large duct PSC.

METHODS

Four classical HLA loci (HLA-A, HLA-B, HLA-C and HLA-DRB1) were genotyped in 87 small duct PSC patients, 485 large duct PSC patients and 1117 controls across three geographical regions.

RESULTS

HLA-DRB1*13:01 (OR = 2.0, 95% CI 1.2-3.4, P = 0.01) and HLA-B*08 (OR = 1.6, 95% CI 1.1-2.4, P = 0.02) were significantly associated with small duct PSC compared with healthy controls. Based on the observed frequency of HLA-B*08 in small duct PSC, the strongest risk factor in large duct PSC, an estimated 32% (95% CI 4-65%) of this population can be hypothesized to represent early stages or mild variants of large duct PSC. This subgroup may be constituted by small duct PSC patients with inflammatory bowel disease (IBD), which greatly resembled large duct PSC in its HLA association. In contrast, small duct PSC without IBD was only associated with HLA-DRB1*13:01(P = 0.03) and was otherwise distinctly dissimilar from large duct PSC.

CONCLUSIONS

Small duct PSC with IBD resembles large duct PSC in its HLA association and may represent early stages or mild variants of large duct disease. Different HLA associations in small duct PSC without IBD could indicate that this subgroup is a different entity. HLA-DRB1*13:01 may represent a specific risk factor for inflammatory bile duct disease.

Hepatobiliary manifestations of inflammatory bowel disease

Patients with inflammatory bowel diseases (IBDs) may present with several hepatic abnormalities. Some of these liver diseases are benign and only require observation, whereas others may cause liver failure and require liver transplantation. The aim of this review was to present and summarize the latest evidence on the most common liver diseases seen in patients with IBD. These manifestations can be divided in to 3 groups: those that are seen in association with IBD, those that are due to metabolic and physiologic changes induced by the IBD and those that are secondary to the drugs used in the treatment of IBD. Primary sclerosing cholangitis is one of the most common hepatobiliary manifestations of IBD that is more prevalent in patients with ulcerative colitis. There is no approved medical treatment for primary sclerosing cholangitis and about 50% of patients will require liver transplantation within 10 to 15 years from the time of diagnosis. Among the drugs that are commonly used in the treatment of IBD, thiopurines and methotrexate impose the higher risk of hepatotoxicity. In most cases, dose adjustment and avoidance of hepatotoxins will normalize the liver tests and discontinuation of the drug is required in a minority of cases. Reactivation of hepatitis B virus during immunosuppressive therapy is a major concern and adequate screening and vaccination is warranted. The approach to a patient with IBD who presents with abnormal liver chemistries can be challenging not only because 2 or more conditions can co-exist but also because management must be individualized.

Update on inflammatory bowel disease in patients with primary sclerosing cholangitis

Patients with primary sclerosing cholangitis (PSC) complicated by inflammatory bowel disease (IBD) represent a distinct subset of patients with unique characteristics, which have serious clinical implications. The aim of this literature review was to shed light to the obscure clinical and molecular aspects of the two diseases combined utilizing current data available and putting issues of diagnosis and treatment into perspective. The prevalence of IBD, mainly ulcerative colitis in PSC patients is estimated to be 21%-80%, dependent on screening programs and nationality. PSC-associated colitis is likely to be extensive, characterized by rectal sparing, backwash ileitis, and generally mild symptoms. It is also more likely to progress to colorectal malignancy, making it imperative for clinicians to maintain a high level of suspicion when tackling PSC patients. There is no optimal surveillance strategy but current guidelines advocate that colonoscopy is necessary at the time of PSC diagnosis with annual endoscopic follow-up. Random biopsies have been criticized and a shift towards targeted biopsies using chromoendoscopy, laser endomicroscopy and narrow-band imaging has been noted. Techniques directed towards genetic mutations instead of histological abnormalities hold promise for easier, more accurate diagnosis of dysplastic lesions. Chemopreventive measures against colorectal cancer have been sought in these patients. Ursodeoxycholic acid seemed promising at first but subsequent studies yielded conflicting results showing anticarcinogenic effects in low doses (8-15 mg/kg per day) and carcinogenic properties in high doses (15-30 mg/kg per day).

Inflammatory bowel disease in patients with primary sclerosing cholangitis: clinical characterization in liver transplanted and nontransplanted patients

BACKGROUND

Inflammatory bowel disease (IBD) in patients with primary sclerosing cholangitis (PSC) seems to differ from IBD without PSC, but a systematic, prospective study of IBD in PSC has until now not been reported. We aimed to describe the clinical, endoscopic, and histopathologic features of PSC-IBD in liver-transplanted and nontransplanted patients.

METHODS

PSC patients (n = 184) were included and underwent ileocolonoscopy with assessment of segmental histopathology.

RESULTS

A total of 155 (84%) patients had IBD, of whom 39 (25%) had undergone colectomy. The patients with an intact colon and complete tissue samples (n = 110) were further investigated. Forty-two (38%) patients had undergone liver transplantation. The median IBD duration was 11 (range, 0-50) years. The majority (65%) had no or sparse IBD symptoms. Inflammatory findings were more frequent by histology than by endoscopy (89% versus 47%, P < 0.001). Histopathological signs of inflammation involved the right colon in 86% of patients and were purely right-sided in 23%. The findings of inflammation were higher in the right compared to the left colon (P < 0.001), but the general inflammatory activity was low. Backwash ileitis was demonstrated in 20% (17/87) of patients and rectal sparing in 65% (70/107). The liver-transplanted patients had lower clinical (P = 0.035) and histological (P = 0.013) IBD activity than the nontransplanted group.

CONCLUSIONS

PSC-IBD may represent a distinct entity of colitis in which low endoscopic activity may mask an active histologic inflammation that possibly contributes to an increased risk of malignancy. Circumstances related to liver transplantation seem to act favorably on colonic inflammation in PSC.

Cutting edge issues in primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory liver disease characterized by the destruction of medium- to large-sized bile ducts and intense concentric fibrosis. Complications from PSC include bacterial cholangitis, cirrhosis, and cholangiocarcinoma and a therapy that might alter the natural history of the disease remains lacking. Our understanding of the pathogenesis of PSC also remains rudimentary but the strong association between PSC and inflammatory bowel disease suggest causal links between the diseases. The male predominance in PSC, lack of a defined, pathogenic auto-antigen, and the potential role of the innate immune system suggest that PSC may be due to dysregulation of immunity rather than a classic autoimmune disease. However, PSC shares several genetic susceptibility loci with other autoimmune diseases including the human leukocyte antigen DRB01*03 haplotype. The precise immune response of PSC is largely unknown but likely involves activation of the innate immune system by bacterial components delivered to the liver via the portal vein. Induction of adhesion molecules and chemokines leads to the recruitment of intestinal lymphocytes. Bile duct injury results from the sustained inflammation and production of inflammatory cytokines. Biliary strictures may cause further damage as a result of bile stasis and recurrent secondary bacterial cholangitis. Progress in our basic understanding of PSC is desperately needed in order to rationally design new therapeutic approaches to this disease.

Pathogenesis of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) represents a chronic cholestatic liver disease with fibroobliterative sclerosis of intra- and/or extrahepatic bile ducts, eventually leading to biliary cirrhosis. The association with human leukocyte antigen (HLA) and non-HLA haplotypes and the presence of autoantibodies in sera of PSC patients support a crucial role for immune-mediated mechanisms in the initiation and progression of PSC. The strong clinical association between PSC and inflammatory bowel diseases led to intriguing pathogenetic concepts, in which the inflamed gut with translocation of bacterial products and homing of gut-primed memory T lymphocytes via aberrantly expressed adhesion molecules plays a fundamental role. Genetically or chemically modified bile composition was shown to induce sclerosing cholangitis and liver fibrosis in a number of animal models ("toxic bile concept"). The potential role of vascular injury with ischemia of bile duct epithelium cells in the development of sclerosing cholangitis is supported by animal models of endothelial cell injury showing close morphological similarities with human PSC.

Sclerosing cholangitis in baboons (Papio spp) resembling primary sclerosing cholangitis of humans

Primary sclerosing cholangitis is a chronic and progressive cholestatic liver disease that has been extensively documented in the human literature. Although it shares many features in common with chronic lymphocytic cholangitis in cats, primary sclerosing cholangitis has never been reported in a nonhuman primate. Primary sclerosing cholangitis is characterized by the presence of intrahepatic and/or extrahepatic inflammation and concentric fibrosis of bile ducts, eventually leading to cirrhosis and hepatic failure. The pathogenesis and cause remain unknown, but the disease likely involves a multifactorial mechanism with genetic- and immune-mediated components. The authors report 2 cases that histologically resemble the condition in humans; they consist of 2 adult male baboons with a clinical history of chronic elevated liver enzymes. In both cases, the liver was histologically characterized by thick bands of fibrosis and mild lymphoplasmacytic periportal cholangiohepatitis with concentric periductal fibrosis, resulting in atrophy and loss of bile ducts. Immunohistochemical analysis revealed positivity of hepatocytes to cytokeratin 7. Masson stain demonstrated marked biliary fibrosis. This is the first report that resembles sclerosing cholangitis in a nonhuman primate, and it suggests that the baboon may provide a useful animal model for this condition in humans.

Primary sclerosing cholangitis is associated with endoscopic and histologic inflammation of the distal afferent limb in patients with ileal pouch-anal anastomosis

BACKGROUND

We hypothesized that patients with primary sclerosing cholangitis (PSC) may have a higher risk for prepouch ileitis in the setting of ileal pouch-anal anastomosis (IPAA). The aim of this study was to compare endoscopic and histologic inflammation in the afferent limb (prepouch ileum) and pouch between IPAA patients with and without PSC.

METHODS

In all, 39 consecutive inflammatory bowel disease (IBD) and IPAA patients with PSC (study group) were identified and 91 IBD and IPAA patients without PSC (control group) were randomly selected with a 1:2 ratio. Demographic, clinical, endoscopic, and histologic variables were analyzed.

RESULTS

There were no significant differences in age, gender, and nonsteroidal antiinflammatory drug use between the study and control groups. Twelve (30.8%) patients in the IPAA-PSC group had coexisting autoimmune disorders, in contrast to five (5.5%) patients in the IPAA control group (P < 0.001). More patients in the study group had endoscopic inflammation as demonstrated by the higher Pouchitis Disease Activity Index (PDAI) endoscopic scores of the afferent limb and pouch body than those in the control group (P = 0.02 and P < 0.001, respectively). In addition, more patients with PSC had higher PDAI histologic scores of the afferent limb than those without PSC (P < 0.001). Multivariate analysis showed higher PDAI endoscopy and histology subscores were associated with risk for PSC, with odds ratio 1.34 (95% confidence interval [CI]: 1.34, 3.79) and 1.61 (95% CI: 1.00, 2.58), respectively.

CONCLUSIONS

Concurrent PSC appears to be associated with a significant prepouch ileitis on endoscopy and histology in patients with IPAA. Pouch patients with long segment of ileitis should be evaluated for PSC.

The prevalence, incidence and natural history of primary sclerosing cholangitis in an ethnically diverse population

BACKGROUND

Primary sclerosing cholangitis (PSC) is a rare chronic cholestatic liver disease often associated with inflammatory bowel diseases (IBD). Current epidemiological data are limited to studies of predominantly Caucasian populations. Our aim was to define the epidemiology of PSC in a large, ethnically diverse US population.

METHODS

The Northern California Kaiser Permanente (KP) database includes records from over 3 million people and was searched for cases of PSC between January 2000 and October 2006. All identified charts were reviewed for diagnosis confirmation, IBD co-morbidity, and major natural history endpoints.

RESULTS

We identified 169 (101 males) cases fulfilling PSC diagnostic criteria with a mean age at diagnosis of 44 years (range 11-81). The age-adjusted point prevalence was 4.15 per 100,000 on December 31, 2005. The age-adjusted incidence per 100,000 person-years was not significantly greater in men 0.45 (95% CI 0.33-0.61) than women 0.37 (95% CI 0.26-0.51). IBD was present in 109/169 (64.5%) cases and was significantly more frequent in men than women with PSC (73.3% and 51.5%, respectively, p = 0.005). The cumulative average yearly mortality rate was 1.9%. Age and serum sodium, creatinine and bilirubin at diagnosis and albumin at last entry were identified as significant factors associated with death, liver transplant or cholangiocarcinoma.

CONCLUSIONS

The incidence and prevalence of PSC observed in a representative Northern California population are lower compared to previous studies in Caucasian populations and this might reflect differences in the incidence of PSC among various ethnic groups.

Electrostatic modifications of the human leukocyte antigen-DR P9 peptide-binding pocket and susceptibility to primary sclerosing cholangitis

The strongest genetic risk factors for primary sclerosing cholangitis (PSC) are found in the human leukocyte antigen (HLA) complex at chromosome 6p21. Genes in the HLA class II region encode molecules that present antigen to T lymphocytes. Polymorphisms in these genes are associated with most autoimmune diseases, most likely because they contribute to the specificity of immune responses. The aim of this study was to analyze the structure and electrostatic properties of the peptide-binding groove of HLA-DR in relation to PSC. Thus, four-digit resolution HLA-DRB1 genotyping was performed in 356 PSC patients and 366 healthy controls. Sequence information was used to assign which amino acids were encoded at all polymorphic positions. In stepwise logistic regressions, variations at residues 37 and 86 were independently associated with PSC (P = 1.2 × 10(-32) and P = 1.8 × 10(-22) in single-residue models, respectively). Three-dimensional modeling was performed to explore the effect of these key residues on the HLA-DR molecule. This analysis indicated that residue 37 was a major determinant of the electrostatic properties of pocket P9 of the peptide-binding groove. Asparagine at residue 37, which was associated with PSC, induced a positive charge in pocket P9. Tyrosine, which protected against PSC, induced a negative charge in this pocket. Consistent with the statistical observations, variation at residue 86 also indirectly influenced the electrostatic properties of this pocket. DRB1*13:01, which was PSC-associated, had a positive P9 pocket and DRB1*13:02, protective against PSC, had a negative P9 pocket.

CONCLUSION

The results suggest that in patients with PSC, residues 37 and 86 of the HLA-DRβ chain critically influence the electrostatic properties of pocket P9 and thereby the range of peptides presented.

Genetics and epigenetics in the fibrogenic evolution of chronic liver diseases

Recent years have seen unprecedented progress in the identification and characterization of genetic information related to chronic liver diseases (CLDs). However, despite the conceptual benefit in early recognition of at-risk populations amenable to pre-emptive treatment and/or surveillance strategies, recent genomic research in the field has placed focus on unravelling the genetic architecture of disease susceptibility, while data on genetic markers anticipating an accelerated fibrogenesis in an individual are still limited. Likewise, sequence variation assigning rapid fibrogenic evolution common to CLDs irrespective of etiology are poorly defined aside from PNPLA3 (adiponutrin) as a prominent exception. The emerging field of epigenetics in hepatology has mostly been studied under the perspective of gene regulation, less so as a heritable alteration in gene activity. In this article we will critically discuss recent findings in genomic hepatology with special focus on the (epi)genetic contribution to the fibrogenic evolution of CLDs.

Primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic bile duct disease leading to fibrotic biliary strictures and liver cirrhosis. The patient population is heterogeneous with regard to disease progression and the presence of co-morbidities, complicating the practical handling of patients as well as studies of pathogenetic mechanisms. The aetiology of PSC is unknown, but the recent findings of several robust susceptibility genes emphasise the importance of genetic risk factors. There is no effective medical treatment available to delay the disease progression, but endoscopic therapy of biliary stenoses may be indicated. Follow-up of patients includes management of the inflammatory bowel disease that is found in the majority of cases along with investigations aimed at the early detection of cholangiocarcinoma and colorectal cancer, which also occur at increased frequencies. In the present review, we aim to summarise the present knowledge of PSC with a particular emphasis on the possible basis of disease variability.

Update on primary sclerosing cholangitis

Early studies in primary sclerosing cholangitis (PSC) were concerned with disease characterization, and were followed by epidemiological studies of PSC and clinical subsets of PSC as well as a large number of treatment trials. Recently, the molecular pathogenesis and the practical handling of the patients have received increasing attention. In the present review we aim to give an update on the pathogenesis of PSC and cholangiocarcinoma in PSC, as well as to discuss the current opinion on diagnosis and treatment of PSC in light of the recent European Association for the Study of the Liver and the American Association for the Study of Liver Diseases practice guidelines.

Unique features of primary sclerosing cholangitis in children

PURPOSE OF REVIEW

To summarize publications on juvenile primary sclerosing cholangitis (PSC) published over the past 5 years. These studies contribute to the understanding of the clinical features, diagnostic pathways, genetic aspects, treatment and outcome of this condition.

RECENT FINDINGS

Sclerosing cholangitis with strong autoimmune features is particularly frequent in paediatric age, where it is more common in girls, responds to immunosuppressive treatment and has a better prognosis than classical PSC. Modern-day magnetic resonance cholangiography allows accurate diagnosis of bile duct disease in most cases. Prolonged oral vancomycin treatment may be beneficial in difficult-to-treat PSC associated with inflammatory bowel disease. Juvenile PSC has a high recurrence rate after liver transplantation. PSC susceptibility and resistance are associated with both human leucocyte antigen-related and unrelated genetic factors.

SUMMARY

Studies on large cohorts of children with PSC are needed for a better understanding of pathogenic mechanisms, response to treatment and outcome of this serious condition.

Pathologic features of ulcerative colitis in patients with primary sclerosing cholangitis: a case-control study

BACKGROUND

The pathologic features of ulcerative colitis (UC) in patients with primary sclerosing cholangitis (PSC) are, essentially, unknown. One previous clinical study suggested that UC-PSC patients reveal a high rate of rectal sparing and backwash ileitis. The purpose of this study was to systematically evaluate the pathologic characteristics and distribution of colonic disease in UC-PSC patients and to compare the results with a matched control group of UC patients without PSC.

METHODS

Forty UC-PSC patients and 40 matched UC patients without PSC (controls) were identified from the files of 3 hospitals between the years 1989 and 2005. Clinical, endoscopic, and follow-up data (including incidence of pouchitis) were evaluated, and a detailed pathologic evaluation of biopsy and resection specimens (when available) was performed in a blinded fashion. The degree of activity and chronicity in mucosal biopsies and/or tissue from resection specimens was graded on a 5-point grading system (0 to 4), and each portion of the colon (cecum, ascending colon, transverse colon, descending colon, rectum) was assessed separately. Rectal sparing and patchiness of disease were evaluated, and scored as either absolute or relative depending on the complete absence of inflammatory disease in the former, or less inflammatory disease in the rectum compared with other parts of the colon in the latter.

RESULTS

In this matched case-control study, UC-PSC patients presented at a significantly earlier age (24.5 y), had a higher prevalence rate of pancolitis (85%), and an overall significantly lower grade of inflammation in the colon (mean grade: 2.09+/-0.085) compared with UC controls (mean age: 33.8 y, pancolitis: 45%, inflammation grade: 2.59+/-0.92, P<0.05 for all comparisons). The incidence rate of absolute and relative rectal sparing (27.5%) and of patchy inflammatory disease proximal to the rectum (5.7%) was not significantly different between the UC-PSC cases and the UC controls (25% and 7.9%, respectively). UC-PSC patients had a higher prevalence rate of ileitis (35.7%) and pouchitis (42.8%), but the values were not significantly different from controls (26.9% and 26.6%, respectively). The incidence rate of dysplasia was similar between the 2 patient groups.

CONCLUSIONS

UC patients with PSC show a propensity for more extensive, but less active, disease but are otherwise characterized by similar pathologic findings compared with UC patients without PSC. Rectal sparing and patchy disease activity is not characteristic of UC patients with PSC.

The immunobiology of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease histologically characterized by the presence of intrahepatic and/or extrahepatic biliary duct concentric, obliterative fibrosis, eventually leading to cirrhosis. Approximately 75% of patients with PSC have inflammatory bowel disease. The male predominance of PSC, the lack of a defined, pathogenic autoantigen, and the potential role of the innate immune system suggest that it may be due to dysregulation of immunity rather than a classic autoimmune disease. However, PSC is associated with several classic autoimmune diseases, and the strongest genetic link to PSC identified to date is with the human leukocyte antigen DRB01*03 haplotype. The precise immunopathogenesis of PSC is largely unknown but likely involves activation of the innate immune system by bacterial components delivered to the liver via the portal vein. Induction of adhesion molecules and chemokines leads to the recruitment of intestinal lymphocytes. Bile duct injury results from the sustained inflammation and production of inflammatory cytokines. Biliary strictures may cause further damage as a result of bile stasis and recurrent secondary bacterial cholangitis. Currently, there is no effective therapy for PSC and developing a rational therapeutic strategy demands a better understanding of the disease.

HLA and autoimmune digestive disease: a clinically oriented review for gastroenterologists

OBJECTIVES

The human leukocyte antigen (HLA) system includes genes involved in graft-vs-host rejection and in immune response. The discovery that HLAs are associated with several diseases led to appealing developments both in basic biomedical research and in clinical medicine, and offered the opportunity to improve the understanding of pathogenesis and classification of diseases, as well as to provide diagnostic and prognostic indicators. The aim of this article is to review the association between HLA alleles and autoimmune digestive disease and its current relationship with modern HLA nomenclature and clinical practice.

METHODS

Articles dealing with the association between HLAs and autoimmune digestive disease (including celiac disease, inflammatory bowel disease, autoimmune hepatitis, sclerosing cholangitis and primary biliary cirrhosis) were searched for using Pubmed and SCOPUS databases from earliest records to January 2008.

RESULTS

The review has provided two sections. In the first, we explain the basic principles of HLA structure, function, and nomenclature, as an introduction to the second section, which describes current associations between HLA alleles and digestive diseases. The clinical implications of each HLA association are critically discussed. Actually, a clinical role for HLA typing is suggested for only a few conditions, e.g., celiac disease.

CONCLUSIONS

The knowledge of current HLA nomenclature and of its association with some digestive diseases such as celiac disease can be useful in clinical practice for diagnostic and prognostic purposes. This can avoid improper HLA typing as well as stressing the need for further studies on other possible clinical applications.

An update on primary sclerosing cholangitis

PURPOSE OF REVIEW

Primary sclerosing cholangitis is a chronic cholestatic liver disease characterized by strictures of the biliary tree complicated by cirrhosis and cholangiocarcinoma. It is immune mediated, although the precise aetiology remains unknown.

RECENT FINDINGS

The research into aetiology, genetic associations, pathogenesis, epidemiology, diagnosis of cholangiocarcinoma and medical treatments are discussed.

SUMMARY

Multiple gene polymorphisms and human leucocyte antigen haplotype associations with primary sclerosing cholangitis have been investigated. Common inflammatory bowel disease associated polymorphisms and ulcerative colitis associated human leucocyte antigen haplotypes are not associated with primary sclerosing cholangitis. Biliary epithelial cells may mediate their own destruction by exaggerating innate and adaptive immune responses to bacterial products in the liver. The natural history of large and small duct primary sclerosing cholangitis has been reviewed. Positron emission tomography may be a useful adjunct to current imaging modalities in the pretransplant assessment of patients to exclude cholangiocarcinoma. Ursodeoxycholic acid remains the most studied medical treatment for primary sclerosing cholangitis; pilot studies suggest a possible role for tacrolimus and silymarin, however further studies are required.

Genetic epidemiology of primary sclerosing cholangitis

The aetiology of primary sclerosing cholangitis (PSC) is not known. A more than 80-fold increased risk of PSC among first-degree relatives emphasizes the importance of genetic factors. Genetic associations within the human leukocyte antigen (HLA) complex on chromosome 6p21 were detected in PSC 25 years ago. Subsequent studies have substantiated beyond doubt that one or more genetic variants located within this genetic region are important. The true identities of these variants, however, remain to be identified. Several candidate genes at other chromosomal loci have also been investigated. However, according to strict criteria for what may be denominated a susceptibility gene in complex diseases, no such gene exists for PSC today. This review summarises present knowledge on the genetic susceptibility to PSC, as well as genetic associations with disease progression and clinical subsets of particular interest (inflammatory bowel disease and cholangiocarcinoma).