A Clinician's Guide to Celiac Disease HLA Genetics

Genetic association between celiac disease and chronic kidney disease: a two-sample Mendelian randomization study

OBJECTIVE

A two-sample Mendelian randomization (MR) analysis was performed to elucidate the causal impact of celiac disease on the risk of chronic kidney disease (CKD).

METHODS

The study comprised data from three genome-wide association studies involving individuals of European ancestry. The study groups included participants with celiac disease (n = 24,269), CKD (n = 117,165), and estimated glomerular filtration rate levels based on serum creatinine (eGFRcrea, n = 133,413). We employed four widely recognized causal inference algorithms: MR-Egger, inverse variance weighted (IVW), weighted median, and weighted mode. To address potential issues related to pleiotropy and overall effects, MR-Egger regression and the MR-PRESSO global test were performed. Heterogeneity was assessed using Cochran's Q test.

RESULTS

We identified 14 genetic variants with genome-wide significance. The MR analysis provided consistent evidence across the various methodologies, supporting a causal relationship between celiac disease and an elevated risk of CKD (odds ratio (OR)IVW = 1.027, p = 0.025; ORweighted median = 1.028, P = 0.049; ORweighted mode = 1.030, p = 0.044). Furthermore, we observed a causal link between celiac disease and a decreased eGFRcrea (ORIVW = 0.997, P = 2.94E-06; ORweighted median = 0.996, P = 1.68E-05; ORweighted mode = 0.996, P = 3.11E-04; ORMR Egger = 0.996, P = 5.00E-03). We found no significant evidence of horizontal pleiotropy, heterogeneity, or bias based on MR-Egger regression, MR-PRESSO, and Cochran's Q test.

CONCLUSION

The results of this study indicate a causal relationship between celiac disease and an increased risk of CKD.

FOXP3 expression in duodenal mucosa: Unique role in pathogenesis and differential diagnosis of celiac disease

Forkhead box protein P3 (FOXP3) positive regulatory T lymphocytes are indispensable in the inflammatory homeostasis of the gastrointestinal tract and represent a significant subset of regulatory cells in inflammatory, autoimmune, and neoplastic conditions. This study aimed to elucidate the potential of FOXP3 expression in diagnosing and pathogenesis of celiac disease (CD) by comparing duodenal biopsies of CD cases with non-CD ones, some of which had increased intraepithelial lymphocytes (IELs). Two hundred sixty-one duodenal tissues of patients who applied to adult gastroenterology were reevaluated for immunohistochemical analysis. After excluding patients on a gluten-free diet (n = 44), the CD (n = 97) and non-CD (n = 120) groups were divided based on clinical complaints that could be associated with CD (intestinal or extraintestinal), serologic and histologic findings. The specific threshold was determined by receiver operating characteristic (ROC) analysis, and its relationship with CD diagnosis and clinicopathological data was evaluated. ROC analysis offered a ">14" cut-off value for diagnosing CD, for which AUC (Area Under The Curve): 0.968, p < 0.0001, sensitivity: 92.8, specificity: 91.7, positive and negative predictive values were 90 % and 94 %, respectively. High FOXP3 expression was associated with higher IEL, diagnosis of CD, more severe histologic (higher Marsh score) and endoscopic (scalloping) findings, and higher anti-tissue transglutaminase and anti-endomysium IgA titers (p < 0.001). It also correlates with IEL in CD patients and is unaffected by the increase in IEL and the presence of gastric Helicobacter Pylori in the non-CD group. FOXP3 is a sensitive and specific marker for diagnosing CD despite inflammatory conditions resulting from non-CD causes.

Exploring the association between microscopic colitis and celiac disease: A comprehensive analysis using the national in-patient data (2016-2019)

BACKGROUND

Several investigations suggested correlation between microscopic colitis (MC) and celiac disease (CD). This study aimed to examine this relationship using large-sized, population-based data with adequate control for confounding factors.

METHODS

This study employed the National Inpatient Sample (NIS) database over 4 years (2016-2019). Patients with/without MC in the presence/absence of CD were identified through ICD-10 codes. Univariate and multi-variate analyses involving odds ratios (OR) and 95% confidence intervals (CI) were performed.

RESULTS

Overall, 26,836,118 patients were analyzed. Of whom, 6,836 patients had MC (n = 179 with CD and n = 6,657 without CD). The mean hospital stay was not significantly different between both groups (5.42 ± 5.44 days vs. 4.95 ± 4.66 days, P = 0.202). The univariate analysis revealed a significant association between MC and CD (OR = 22.69, 95% [19.55, 26.33], P < 0.0001). In the multi-variate analysis, which adjusted for potential confounders including age, race, hospital region, hospital teaching status, ZIP income, smoking status, alcohol overuse, hypertension, diabetes mellitus, lipidemia-related disorders, non-steroidal anti-inflammatory drug use, and selected auto-immune diseases, the association remained significant (OR = 15.71, 95% CI [13.52, 18.25], P < 0.0001). Moreover, in patients with MC, the presence of CD emerged as a significant, independent variable of in-hospital mortality in univariate (OR = 2.87, 95% [1.14, 7.21], P = 0.025) and multi-variate (OR = 3.37, 95% CI [1.32, 8.60], P = 0.011) analyses.

CONCLUSION

This study establishes a probable link between MC and CD, backed by both univariate and multi-variate analyses, while also identifying CD as an independent risk factor for increased mortality among MC patients. These findings need to be validated in real-world clinical studies.

The Humoral Immune Response against Human Endogenous Retroviruses in Celiac Disease: A Case-Control Study

BACKGROUND

Celiac disease (CD) is an immune-mediated disease characterized by disruptions of the small intestine. Factors such as viral and bacterial infections can trigger CD. Recently, the reactivation of Human Endogenous Retroviruses (HERVs) has also been implicated, but little is known about their specific role in patients with celiac disease.

METHODS

The purpose of this study is to explore the humoral immune response mounted against epitopes derived from the envelope portion of three families of HERVs (HERV-K, HERV-H, and HERV-W) in CD patients. Reactivity against the HERV-K, HERV-H, and HERV-W env-su peptides was tested by indirect ELISAs in plasma of 40 patients with celiac disease and 41 age-matched healthy subjects (HCs).

RESULTS

HERV-K, HERV-H, and HERV-W env-su peptides triggered different antibody responses in CD patients compared to HCs, with a stronger reactivity (p = 0.0001).

CONCLUSIONS

Present results show, for the first time, that epitopes of HERV-K, HERV-H, and HERV-W are more recognized in patients with CD. Taking into consideration their proinflammatory and autoimmune features, this might suggest that HERVs may contribute to the development of CD or its exacerbation in genetically predisposed subjects. Finally, to elucidate the interplay between gut inflammation and HERVs during the inflammatory process, further studies are required. Those investigations should focus on the expression levels of HERVs and their relationship with the immune response, specifically examining anti-transglutaminase 2 (TG2) antibody levels under both gluten-free and gluten-containing dietary conditions.

Celiac Disease, Gluten Sensitivity, and Diet Management

PURPOSE OF REVIEW

Celiac disease is a common chronic inflammatory condition of the small bowel triggered by gluten in wheat, rye and barley in the diet. Non-celiac gluten sensitivity presents with symptoms similar to celiac disease with the ingestion of gluten or other components of wheat. In this article, we review challenges presented by a gluten free diet for the treatment of both disorders.

RECENT FINDINGS

Wheat is ubiquitous in the diet and medications/products. A registered dietitian is mandatory for patient education on the gluten free diet. Naturally gluten free foods provide a healthy diet for those with celiac disease. Whole grains labelled gluten free, including oats, are encouraged in the diet as refined grains may be deficient in fiber, protein, and micronutrients, particularly folate. Gluten contamination is the most common cause of persistent symptoms in celiac disease though shared equipment of food preparation may not be as large a problem as suspected. Most with celiac disease on a gluten free diet will fully recover and gain weight that poses a problem for those overweight to start. The gluten free diet may have a negative impact on quality of life for both celiac patients and their families. Those with hypervigilance of the gluten free diet and avoidance of dining out have the lowest quality of life. The gluten free diet is currently the only effective treatment for celiac disease. A registered dietitian is needed to educate patients on the complexity of the gluten free diet with a goal of healthy eating, maintaining a healthy weight, and avoiding disordered eating or diet hypervigilance; key to a good quality of life.

γδ+ T-Cells Is a Useful Biomarker for the Differential Diagnosis between Celiac Disease and Non-Celiac Gluten Sensitivity in Patients under Gluten Free Diet

BACKGROUND

The differential diagnosis between patients with celiac disease (CD) and non-celiac gluten sensitivity (NCGS) is difficult when a gluten-free diet (GFD) has been initiated before the diagnostic work-up. Isolated increases in TCRγδ+ and celiac lymphogram (increased TCRγδ+ plus decreased CD3-) may enable differential diagnosis in this challenging clinical setting. This study evaluated: (1) the accuracy of %TCRγδ+ and celiac lymphogram for diagnosing CD before and after GFD and for differentiation with NCGS; (2) TCRγδ+ kinetics at baseline and after starting GFD in both CD and NCGS.

METHODS

The inclusion criteria were patients with CD (n = 104), NCGS (n = 37), and healthy volunteers (n = 18). An intestinal biopsy for intraepithelial lymphogram by flow cytometry was performed at baseline and after GFD. The optimal cutoff for CD diagnostic accuracy was established by maximizing the Youden index and via logistic regression.

RESULTS

%TCRγδ+ showed better diagnostic accuracy than celiac lymphogram for identifying CD before and after GFD initiation. With a cutoff > 13.31, the accuracy for diagnosing CD in patients under GFD was 0.88 [0.80-0.93], whereas the accuracy for diagnosing NCGS (%TCRγδ+ ≤ 13.31) was 0.84 [0.76-0.89]. The percentage of TCRγδ+ cells showed differential kinetics between CD (baseline 22.7% [IQR, 16.4-33.6] vs. after GFD 26.4% [IQR, 17.8-36.8]; p = 0.026) and NCGS (baseline 9.4% [IQR, 4.1-14.6] vs. after GFD 6.4% [IQR, 3.2-11]; p = 0.022).

CONCLUSION

TCRγδ+ T cell assessment accurately diagnoses CD before and after a GFD. Increased TCRγδ+ was maintained in the long term after GFD in CD but not in NCGS. Altogether, this suggests the potential usefulness of this marker for the differential diagnosis of these two entities in patients on a GFD.

Vitamin D: An Essential Nutrient in the Dual Relationship between Autoimmune Thyroid Diseases and Celiac Disease-A Comprehensive Review

Autoimmune thyroid diseases (AITD) are among the most frequent autoimmune disorders, with a multifactorial etiology in which both genetic and environmental determinants are probably involved. Celiac disease (CeD) also represents a public concern, given its increasing prevalence due to the recent improvement of screening programs, leading to the detection of silent subtypes. The two conditions may be closely associated due to common risk factors, including genetic setting, changes in the composition and diversity of the gut microbiota, and deficiency of nutrients like vitamin D. This comprehensive review discussed the current evidence on the pivotal role of vitamin D in modulating both gut microbiota dysbiosis and immune system dysfunction, shedding light on the possible relevance of an adequate intake of this nutrient in the primary prevention of AITD and CeD. While future technology-based strategies for proper vitamin D supplementation could be attractive in the context of personalized medicine, several issues remain to be defined, including standardized assays for vitamin D determination, timely recommendations on vitamin D intake for immune system functioning, and longitudinal studies and randomized controlled trials to definitely establish a causal relationship between serum vitamin D levels and the onset of AITD and CeD.

UK NEQAS and BSHI guideline: Laboratory testing and clinical interpretation of HLA genotyping results supporting the diagnosis of coeliac disease

Coeliac disease is a common immune-mediated inflammatory disorder caused by dietary gluten in genetically susceptible individuals. While the diagnosis of coeliac disease is based on serological and histological criteria, HLA-DQ genotyping can be useful, especially in excluding the diagnosis in patients who do not carry the relevant DQ heterodimers: DQA1*05 DQB1*02, DQB1*03:02 or DQA1*02 DQB1*02 (commonly referred to as DQ2.5, DQ8 and DQ2.2, respectively). External quality assessment results for HLA genotyping in coeliac disease have revealed concerning errors in HLA genotyping, reporting and clinical interpretation. In response, these guidelines have been developed as an evidence-based approach to guide laboratories undertaking HLA genotyping for coeliac disease and provide recommendations for reports to standardise and improve the communication of results.

Zonulin as a Biomarker for the Development of Celiac Disease

OBJECTIVES

Increased intestinal permeability seems to be a key factor in the pathogenesis of autoimmune diseases, including celiac disease (CeD). However, it is unknown whether increased permeability precedes CeD onset. This study's objective was to determine whether intestinal permeability is altered before celiac disease autoimmunity (CDA) in at-risk children. We also examined whether environmental factors impacted zonulin, a widely used marker of gut permeability.

METHODS

We evaluated 102 children in the CDGEMM study from 2014-2022. We included 51 CDA cases and matched controls, who were enrolled for 12 months or more and consumed gluten. We measured serum zonulin from age 12 months to time of CDA onset, and the corresponding time point in controls, and examined clinical factors of interest. We ran a mixed-effects longitudinal model with dependent variable zonulin.

RESULTS

Children who developed CDA had a significant increase in zonulin in the 18.3 months (range 6-78) preceding CDA compared to those without CDA (slope differential = β = 0.1277, 95% CI: 0.001, 0.255). Among metadata considered, zonulin trajectory was only influenced by increasing number of antibiotic courses, which increased the slope of trajectory of zonulin over time in CDA subjects (P = .04).

CONCLUSIONS

Zonulin levels significantly rise in the months that precede CDA diagnosis. Exposure to a greater number of antibiotic courses was associated with an increase in zonulin levels in CDA subjects. This suggests zonulin may be used as a biomarker for preclinical CeD screening in at-risk children, and multiple antibiotic courses may increase their risk of CDA by increasing zonulin levels.

HLA-DQ2/8 and COVID-19 in Celiac Disease: Boon or Bane

The SARS-CoV-2 pandemic continues to pose a global threat. While its virulence has subsided, it has persisted due to the continual emergence of new mutations. Although many high-risk conditions related to COVID-19 have been identified, the understanding of protective factors remains limited. Intriguingly, epidemiological evidence suggests a low incidence of COVID-19-infected CD patients. The present study explores whether their genetic background, namely, the associated HLA-DQs, offers protection against severe COVID-19 outcomes. We hypothesize that the HLA-DQ2/8 alleles may shield CD patients from SARS-CoV-2 and its subsequent effects, possibly due to memory CD4 T cells primed by previous exposure to human-associated common cold coronaviruses (CCC) and higher affinity to those allele's groove. In this context, we examined potential cross-reactivity between SARS-CoV-2 epitopes and human-associated CCC and assessed the binding affinity (BA) of these epitopes to HLA-DQ2/8. Using computational methods, we analyzed sequence similarity between SARS-CoV-2 and four distinct CCC. Of 924 unique immunodominant 15-mer epitopes with at least 67% identity, 37 exhibited significant BA to HLA-DQ2/8, suggesting a protective effect. We present various mechanisms that might explain the protective role of HLA-DQ2/8 in COVID-19-afflicted CD patients. If substantiated, these insights could enhance our understanding of the gene-environment enigma and viral-host relationship, guiding potential therapeutic innovations against the ongoing SARS-CoV-2 pandemic.

A Clinician's Guide to Gluten Challenge

Gluten challenge is an essential clinical tool that involves reintroducing or increasing the amount of gluten in the diet to facilitate diagnostic testing in celiac disease (CD). Nevertheless, there is no consensus regarding the applications of gluten timing, dosing, and duration in children. This review aims to summarize the current evidence, discuss practical considerations, and proposes a clinical algorithm to help guide testing in pediatric patients. Childhood development, social circumstances, and long-term health concerns must be considered when identifying a candidate for gluten challenge. Based on previous studies, the authors suggest baseline serology followed by a minimum of 3-6 grams of gluten per day for over 12 weeks to optimize diagnostic accuracy for evaluation of CD. A formal provider check-in at 4-6 weeks is essential so the provider and family can adjust dosing or duration as needed. Increasing the dose of gluten further may improve diagnostic yield if tolerated, although in select cases a lower dose and shorter course (6-12 weeks) may be sufficient. There is consensus that mild elevations in celiac serology (<10 times the upper limit of normal) or symptoms, while supportive are not diagnostic for CD. Current North American Society for Pediatric Gastroenterology, Hepatology and Nutrition guidelines recommend histologic findings of intraepithelial lymphocytosis, crypt hyperplasia, and villous atrophy as the accurate and most appropriate endpoint for gluten challenge.

Updates in the diagnosis and management of coeliac disease

Coeliac disease is a common autoimmune disorder induced by ingesting gluten, the protein component of wheat, barley, and rye. It is estimated that one-in-hundred people worldwide have coeliac disease, of whom the majority remain undiagnosed. Coeliac disease is characterized by a wide range of gastrointestinal and extraintestinal symptoms but can also present asymptomatically. Diagnosing coeliac disease depends on the concordance of clinical, serological and histopathological data. However, the diagnosis can be challenging and frequently overlooked. Undiagnosed coeliac disease is associated with an increased risk of complications and detrimental effects on quality of life. Early diagnosis and treatment of coeliac disease are necessary to reduce the risk of long-term complications.

Prevalence and detection rate of celiac disease in Italy: Results of a SIGENP multicenter screening in school-age children

BACKGROUND

Celiac disease is a common lifelong disorder. Recent studies indicate that the number of clinically detected cases has increased over the last decades, however little is known about changes in the prevalence and the detection rate of celiac disease.

AIM

To evaluate the current prevalence and detection rate of celiac disease in Italy by a multicenter, mass screening study on a large sample of school-age children.

METHODS

children aged 5-11 years were screened at school by HLA-DQ2 and -DQ8 determination on a drop of blood in six Italian cities; total serum IgA and IgA anti-transglutaminase were determined in children showing HLA-DQ2 and/or -DQ8 positivity. Diagnosis of celiac disease was confirmed according to the European guidelines.

RESULTS

5994 children were eligible, 4438 participated and 1873 showed predisposing haplotypes (42.2%, 95% CI=40.7-43.7). The overall prevalence of celiac disease was 1.65% (95% CI, 1.34%-2.01%). Only 40% of celiac children had been diagnosed prior to the school screening. Symptoms evoking celiac disease were as common in celiac children as in controls.

CONCLUSION

In this multicenter study the prevalence of celiac disease in school-age Italian children was one of the highest in the world. Determination of HLA predisposing genotypes is an easy and fast first-level screening test for celiac disease. Without a mass screening strategy, 60% of celiac patients remain currently undiagnosed in Italy.

The debate in the diagnosis of coeliac disease - time to go 'no-biopsy'?

PURPOSE OF REVIEW

Duodenal biopsies have been central to making a diagnosis of coeliac disease for the last 70 years. Recent paediatric guidelines have reduced the emphasis on duodenal biopsies with the incorporation of a 'no-biopsy' arm to the diagnostic pathway. This review discusses the no-biopsy approach in adults and highlights advances in alternative (non-biopsy) diagnostic modalities in coeliac disease.

RECENT FINDINGS

Evidence suggests that a no-biopsy approach for the diagnosis of adult coeliac disease is accurate. However, a number of factors still favour duodenal biopsy sampling in specific patient groups. Moreover, several factors need to be considered if this pathway is implemented into local gastroenterology services.

SUMMARY

Duodenal biopsies remain an important step in the diagnosis of adult coeliac disease. However, an alternative approach that removes the necessity for biopsies may be an option in selected adults. If further guidelines incorporate this pathway, then efforts should focus on supporting a dialogue between primary and secondary care to facilitate the appropriate implementation of this approach.

Predictive Biomarkers for Checkpoint Inhibitor Immune-Related Adverse Events

Immune-checkpoint inhibitors (ICIs) are antagonists of inhibitory receptors in the immune system, such as the cytotoxic T-lymphocyte-associated antigen-4, the programmed cell death protein-1 and its ligand PD-L1, and they are increasingly used in cancer treatment. By blocking certain suppressive pathways, ICIs promote T-cell activation and antitumor activity but may induce so-called immune-related adverse events (irAEs), which mimic traditional autoimmune disorders. With the approval of more ICIs, irAE prediction has become a key factor in improving patient survival and quality of life. Several biomarkers have been described as potential irAE predictors, some of them are already available for clinical use and others are under development; examples include circulating blood cell counts and ratios, T-cell expansion and diversification, cytokines, autoantibodies and autoantigens, serum and other biological fluid proteins, human leucocyte antigen genotypes, genetic variations and gene profiles, microRNAs, and the gastrointestinal microbiome. Nevertheless, it is difficult to generalize the application of irAE biomarkers based on the current evidence because most studies have been retrospective, time-limited and restricted to a specific type of cancer, irAE or ICI. Long-term prospective cohorts and real-life studies are needed to assess the predictive capacity of different potential irAE biomarkers, regardless of the ICI type, organ involved or cancer site.

"Geographical distribution of risk genotypes in pediatric patients with celiac disease in Spain"

Celiac disease is strongly associated with HLA DQ, specifically with haplotypes. DRB1*03-DQA1*05:01/DQB1*02:01 (DQ2.5),DRB1*07-DQA1*02:01/DQB1*02:02 (DQ2.2), DRB1*11-DQA1*05:05/DQB1*03:01 (DQ7.5), and DRB1*04-DQA1*03:01/DQB1*03:02 (DQ8). The distribution of these risk haplotypes in patients with celiac disease is different in the geographical areas investigated. A high frequency of DRB1*07- DQA1*02:01/DQB1*02:02 (DQ2.2) and DRB1*11-DQA1*05:05/DQB1*03:01 (DQ7.5), has been described in Southern Europe. We analyzed 2102 confirmed CD cases with information on both DQB1* alelles and their distribution by geographical area in Spain. According to the presence of this haplotype in one or two chromosomes, the genotype is classified in: DQ2 homozygous, DQ2 heterozygous (cis or trans), DQ8 homozygous, DQ8/DQ2.5, DQ 2.2 homozygous and genotype known as "half DQ2". Two different patterns of risks related to CD were identified. In the Basque Country and Navarre, the Mediterranean Area (Aragon, Catalonia, Valencia, Balearic Islands, and Murcia), the South of Spain (Andalucía and Extremadura), and the Canary Islands, higher frequency of DQ2.5 trans, and more than 80% of DQ2.5/DQ2.2 homozygosis were described. The Cantabrian Coast (Cantabria, Asturias, and Galicia) and Central Areas (Castilla-León and Castilla-La Mancha) showed a higher percentage of DQ2.5/DQ2.5 homozygosis and a lower DQ2.5 in trans frequency, as in Northern Europe. Madrid has an intermediate model between the two described above. 17 cases (0.8%) did not carry any CD risk haplotypes.

Choosing which in-hospital laboratory tests to target for intervention: a scoping review

INTRODUCTION

Some laboratory testing practices may be of low value, leading to wasted resources and potential patient harm. Our scoping review investigated factors and processes that developers report using to inform decisions about what tests to target for practice improvement.

METHODS

We searched Medline on May 30th, 2019 and June 28th, 2021 and included guidelines, recommendation statements, or empirical studies related to test ordering practices. Studies were included if they were conducted in a tertiary care setting, reported making a choice about a specific test requiring intervention, and reported at least one factor informing that choice. We extracted descriptive details, tests chosen, processes used to make the choice, and factors guiding test choice.

RESULTS

From 114 eligible studies, we identified 30 factors related to test choice including clinical value, cost, prevalence of test, quality of test, and actionability of test results. We identified nine different processes used to inform decisions regarding where to spend intervention resources.

CONCLUSIONS

Intervention developers face difficult choices when deciding where to put scarce resources intended to improve test utilization. Factors and processes identified here can be used to inform a framework to help intervention developers make choices relevant to improving testing practices.

Celiac Disease Genetics, Pathogenesis, and Standard Therapy for Japanese Patients

Celiac disease is an autoimmune disease primarily affecting the small intestine that is caused by the ingestion of gluten in genetically susceptible individuals. The development of celiac disease is based on a complex immune response to gluten proteins. The global average prevalence in the general population is about 1%. In recent years, it has become clear that celiac disease is not less common in Asian countries than in Western countries but often remains undiagnosed. Although the number of patients with celiac disease in Asia is expected to increase with improving disease recognition and advances in diagnostic techniques, there remain few reports of celiac disease in the Far East region of Asia, especially in Japan. In this paper, we outline the epidemiology, diagnosis, and treatment of celiac disease. In addition, we summarize the reported Japanese cases of celiac disease with an overview in Japan.

Meta-Analysis and Systematic Review of HLA DQ2/DQ8 in Adults with Celiac Disease

Although people with human leukocyte antigens (HLA) DQ2 and/or DQ8 are more likely to develop celiac disease (CD), the condition cannot be fully explained by this genetic predisposition alone. Multiple, as yet unidentified, factors contribute to the genesis of CD, including genetics, the environment, and the immune system. In order to provide insight into a prospective possibility and an expanded screening technique, we aim to undertake a comprehensive and meta-analytical study of the assessment and distribution of HLA class II (HLA-DQ2/DQ8) in adult CD patients. A systematic review was conducted using an electronic search of databases (PubMed, Google Scholar, Embase, and Direct Science) from January 2004 to February 2022. DQ2/DQ2 homozygotes have the highest risk of developing CD. DQ2/DQ8 typing is an effective test to exclude CD from the differential diagnosis of a patient with CD symptoms. Although other non-HLA genes have been associated with CD, they are rarely considered at diagnosis because they account for only a small proportion of the heritability of CD. This finding, together with the information gathered previously, may be useful in considering widely available and economically feasible screening options for celiac disease in young people.

Celiac Disease Predisposition and Genital Tract Microbiota in Women Affected by Recurrent Pregnancy Loss

The incidence of Idiopathic Recurrent Pregnancy Loss (RPL) is doubled in patients suffering from Celiac Disease (CD) compared to healthy populations. CD genetic components are HLA class II genes known as HLA-DQ2 and DQ8. Genetically susceptible women can remain asymptomatic even though they are exposed to a doubled risk of RPL compared to the general population. Furthermore, CD has been associated with microbiota alterations. The aim of this study is to evaluate endometrial and vaginal microbiota in HLA-DQ2/DQ8 positive and negative RPL patients compared to healthy pregnant women. Endometrial and vaginal microbiota of 3 subgroups were evaluated: 15 HLA-DQ2/DQ8 positive RPL women, 25 HLA DQ2/DQ8 negative RPL women (for a total of 40 RPL women) and 7 healthy fertile controls with previous uncomplicated pregnancies (all HLA-DQ2/DQ8 negative). The 2 RPL subgroups (HLA-DQ2/DQ8 positive and negative) showed a different endometrial and vaginal composition in the Lactobacillacae family compared to controls: Lactobacillus acidophilus was absent both in the vaginal and endometrial samples of RPL women, while Lactobaciluus iners, which can favor a less stable vaginal microbiota, was found only in RPL women (26.4% in HLA DQ2/DQ8 positive and 22.1% HLA DQ2/DQ8 negative) in both the vaginal and endometrial districts. In conclusion, both HLA DQ2/DQ8 positive-RPL and HLA DQ2/DQ8 negative-RPL women showed different endometrial and vaginal microbiota composition compared to healthy controls.

HLA-DQ genotype distribution and risk evaluation of celiac disease in Northwest China

BACKGROUND

Celiac disease (CD) is an autoimmune small bowel disease. Genetic susceptibility for CD is mainly determined by the human leukocyte antigen (HLA)-DQ haplotypes. The risk of CD conferred by HLA genotypes varies geographically and across populations, however, this has not yet been documented in Chinese patients with CD.

AIMS

To investigate the distribution of HLA-DQ and the related risks of CD development in Northwest China.

METHODS

A total of 75 CD patients and 300 healthy individuals were genotyped for HLA-DQ using the Illumina NextSeq, and the relative risks of the different genotypes were evaluated.

RESULTS

In total, 68.00% of CD patients and 21.00% of controls carried HLA-DQ2.5 heterodimers (p < 0.001). We identified four CD risk gradients. Individuals carrying a double dose of DQB1*02 had the highest risk of developing CD (1:16); however, with heterozygosis (DQB1*02:02/DQB1*02:01) having the highest risk (1:9). HLA-DQ2.5 individuals with a single copy of HLA-DQB1*02, in either the cis or trans configuration, were at a medium risk (1:38). Non-DQ2.5 carriers of DQ8 or DQ2.2 were at low risk, while only carriers of DQ7.5 or DQX.5 were at very low risk. Patients with the HLA-DQ2.5 genotype had more severe mucosal damage compared with the HLA-DQ2.5 genotype negative CD patients (70.59% vs. 41.67%, p = 0.016).

CONCLUSION

Genetic susceptibility to CD is highly prevalent in the Northwest Chinese population and the highest risk of developing CD was associated with the DQ2.5/DQ2.2 genotype. The DQ2.5 allele is involved in the severity of mucosal injury.

Phenome of coeliac disease vs. inflammatory bowel disease

Coeliac disease (CeD) is characterized by gliadin-induced intestinal inflammation appearing in genetically susceptible individuals, such as HLA-DQ2.5 carriers. CeD, as well as other chronic intestinal disorders, such as Crohn's disease (CD) and ulcerative colitis, has been associated with increased morbidity and mortality, but the causes are unknown. We systematically analysed CeD-associated diagnoses and compared them to conditions enriched in subjects with CD/UC as well as in HLA-DQ2.5 carriers without CeD. We compared the overall and cause-specific mortality and morbidity of 3,001 patients with CeD, 2,020 with CD, 4,399 with UC and 492,200 controls in the community-based UK Biobank. Disease-specific phenotypes were assessed with the multivariable Phenome Wide Association Study (PheWAS) method. Associations were adjusted for age, sex and body mass index. All disease groups displayed higher overall mortality than controls (CD: aHR = 1.91[1.70-2.17]; UC: aHR = 1.32 [1.20-1.46]; CeD: aHR = 1.38 [1.22-1.55]). Cardiovascular and cancer-related deaths were responsible for the majority of fatalities. PheWAS analysis revealed 166 Phecodes overrepresented in all three disorders, whereas only ~ 20% of enriched Phecodes were disease specific. Seven of the 58 identified CeD-specific Phecodes were enriched in individuals homozygous for HLA-DQ2.5 without diagnosed CeD. Four out of these seven Phecodes and eight out of 19 HLA-DQ2.5 specific Phecodes were more common in homozygous HLA-DQ2.5 subjects with vs. without CeD, highlighting the interplay between genetics and diagnosis-related factors. Our study illustrates that the morbidity and mortality in CeD share similarities with CD/UC, while the CeD-restricted conditions might be driven by both inherited and acquired factors.

Review article: Becoming and being coeliac-special considerations for childhood, adolescence and beyond

Classically considered a disease of early childhood characterised by malabsorption and failure to thrive, coeliac disease is now recognised to arise in genetically susceptible individuals at any age. Although permissive HLA genotypes are the strongest predictor of coeliac disease, they are not sufficient. Several prospective cohort studies enrolling genetically at-risk infants have investigated the role of potential triggers of coeliac disease autoimmunity, such as timing of gluten introduction, viral infections and dietary patterns. Much less is known about triggers of coeliac disease in adulthood. Better understanding of factors leading to coeliac disease may be helpful in the management of those with potential coeliac disease (elevated serum celiac antibodies without villous atrophy in the small intestine), many of whom initiate a gluten-free diet without demonstration of villous atrophy. There are a range of clinical presentations of celiac disease in childhood and patterns of coeliac serology, including fluctuation and spontaneous reversion on a gluten-containing diet, vary. There is a current debate over best strategies to manage adults and children with potential coeliac disease to avoid over-treatment and under-treatment. Childhood and adolescence carry unique issues pertaining to the diagnosis and management of coeliac disease, and include nutrition and growth, rescreening, repeat biopsy, dietary adherence concerns and transition to adult care. In conclusion, while coeliac disease has similar pathogenesis and general clinical manifestations in paediatric and adult populations, diagnostic and management approaches need to adapt to the developmental stages.

Coeliac disease

Coeliac disease is an autoimmune disorder that primarily affects the small intestine, and is caused by the ingestion of gluten in genetically susceptible individuals. Prevalence in the general population ranges from 0·5% to 2%, with an average of about 1%. The development of the coeliac enteropathy depends on a complex immune response to gluten proteins, including both adaptive and innate mechanisms. Clinical presentation of coeliac disease is highly variable and includes classical and non-classical gastrointestinal symptoms, extraintestinal manifestations, and subclinical cases. The disease is associated with a risk of complications, such as osteoporosis and intestinal lymphoma. Diagnosis of coeliac disease requires a positive serology (IgA anti-transglutaminase 2 and anti-endomysial antibodies) and villous atrophy on small-intestinal biopsy. Treatment involves a gluten-free diet; however, owing to the high psychosocial burden of such a diet, research into alternative pharmacological treatments is currently very active.

Association between idiopathic pulmonary hemosiderosis and celiac disease in pediatric patients: A scoping review of the literature over the past 50 years

INTRODUCTION

Idiopathic pulmonary hemosiderosis (IPH) is a rare cause of diffuse alveolar hemorrhage, the mechanism of which is currently unknown. Nearly one-third of pediatric patients with IPH test positive for Celiac disease (CD) serology. Several hypothetical mechanisms have been proposed to unify the coexistence of these two entities, also referred to as Lane-Hamilton syndrome (LHS).

METHOD

This manuscript is a scoping review of the medical literature. Medline, Embase, and PubMed Central databases were searched between 1971 and 2021 with appropriate search words to identify all cases of pediatric LHS.

RESULTS

A total of 20 manuscripts with 23 pediatric patients with LHS were identified. The mean age was 11 years, and 13/23 (56.5%) of the children were boys. Hemoptysis was present in 57% of patients during diagnosis. Bronchoscopy with bronchoalveolar lavage demonstrating hemosiderin laden macrophages was the primary mode of diagnostic confirmation. Only three patients underwent lung biopsy. Any significant GI symptom was reported in a minority of patients (22%). Iron deficiency anemia on presentation was described in 83% of children. The majority of patients were malnourished. Serology for CD was positive in all patients, as was the histopathologic analysis of the small bowel biopsy. No patients had any other autoantibody positivity. The introduction of gluten free diet (GFD) was associated with a positive response in 20/23 patients.

CONCLUSION

All pediatric patients with IPH should undergo screening for CD. Low serum ferritin in patients with IPH could be suggestive of coexisting CD. Strict GFD should be tried as the initial therapy.

Ultra-short celiac disease exhibits differential genetic and immunophenotypic features compared to conventional celiac disease

BACKGROUND

Ultra-short coeliac disease (USCD) is a novel celiac disease (CD) subtype limited to the duodenal bulb (D1). HLA haplotypes and flow cytometry have not been assessed yet.

AIMS

To compare genetic, clinical, serologic, histopathologic and inmmunophenotypic parameters between USCD and conventional celiac disease (CCD) patients.

METHODS

Prospective single-center study in children and adult patients undergoing duodenal biopsies on a gluten-containing diet. Biopsies for histology and flow cytometry were taken separately from D1 and distal duodenum. Biopsies in seronegative patients with celiac lymphogram were repeated after 2 years on a gluten-free diet.

RESULTS

Among 505 included patients, 127 were diagnosed with CD, of whom 7 (5.5%) showed USCD. HLADQ2 was significantly less common in USCD compared to CCD (71% vs. 95%, p 0.003). Likewise, USCD patients showed more frequent non-significant seronegativity (28% vs. 8%, p 0.07) and significantly lower titrations (7-15 IU/ml) of tissue transglutaminase antibodies (tTG-IgA) (60% vs. 13%, p<0.001). Biopsies from D1 revealed significant less NK cells down-expression in USCD patients (1.4 vs. 5, p 0.04).

CONCLUSIONS

Up to 5.5% of CD patients showed USCD. A lower frequency of HLADQ2, along with less serum tTG-IgA titration and duodenal NK cell suppression, were differential features of USCD.

Seronegative Celiac Disease in Patients with Isolated Refractory Dyspepsia and Gastroesophageal Reflux Disease

Background/Aims

To investigate the presence of seronegative celiac disease in patients with isolated refractory dyspepsia and gastroesophageal reflux disease (GERD)-related complaints.

Methods

This was a single-center, prospective study performed at a tertiary care referral hospital. Among 968 consecutive patients, 129 seronegative patients with tissue damage consistent with Marsh IIIa classification or above were included. The patients were divided into two groups dyspepsia (n=78) and GERD (n=51). Biopsies were taken from the duodenum regardless of endoscopic appearance, and patients with Marsh IIIa or above damage were advised to consume a gluten-free diet. The Glasgow Dyspepsia Severity (GDS) score, Reflux Symptom Index (RSI), and Biagi score were calculated at baseline and every 3 months. Control endoscopy was performed every 6 months during follow-up.

Results

The median follow-up time was 19.9 months (range, 6 to 24 months) in the dyspepsia group and 19.2 months (range, 6 to 24 months) in the GERD group. All the patients were positive for the HLA-DQ2 and DQ8 haplotypes. The differences between the mean GDS scores (14.3±2.1 vs 1.1±0.2, respectively, p<0.05), RSI scores (6.3±0.8 vs 0.7±0.1, respectively, p<0.05), and Biagi scores (3.1±0.4 vs 0.7±0.3 in the dyspepsia group and 2.5±0.4 vs 0.5±0.2 in GERD group) before and after implementation of the gluten-free diet were statistically significant. The decreases in the scores were consistent with improvements in the histological findings. There was no significant correlation between endoscopic appearance and histological examination results (p=0.487).

Conclusions

Seronegative celiac disease may be considered in this group of patients. Even if a patient is seronegative and has normal endoscopic findings, duodenal biopsy should be considered.

How does a celiac iceberg really float? The relationship between celiac disease and gluten

Celiac disease (CD) is an autoimmune intestinal disease caused by intolerance of genetically susceptible individuals after intake of gluten-containing grains (including wheat, barley, etc.) and their products. Currently, CD, with "iceberg" characteristics, affects a large population and is distributed over a wide range of individuals. This present review summarizes the latest research progress on the relationship between CD and gluten. Furthermore, the structure and function of gluten peptides related to CD, gluten detection methods, the effects of processing on gluten and gluten-free diets are emphatically reviewed. In addition, the current limitations in CD research are also discussed. The present work facilitates a comprehensive understanding of CD as well as gluten, which can provide a theoretical reference for future research.

Insights into the underlying mechanisms and clinical management of microscopic colitis in relation to other gastrointestinal disorders

Microscopic colitis (MC) is a chronic inflammatory disease of the large intestine and as a relatively late recognized condition, its relationship with other disorders of the gastrointestinal tract is gradually being understood and investigated. As a multifactorial disease, MC interacts with inflammatory bowel disease, celiac disease, and irritable bowel syndrome through genetic overlap, immunological factors, and gut microflora. The risk of colorectal cancer was significantly lower in MC, gastrointestinal infections increased the risk of developing MC, and there was an inverse association between Helicobacter pylori infection and MC. A variety of associations are found between MC and other gastrointestinal disorders, where aspects such as genetic effects, resemblance of immunological profiles, and intestinal microecology are potential mechanisms behind the relationships. Clinicians should be aware of these connections to achieve a better understanding and management of MC.

The double-edged sword of gut bacteria in celiac disease and implications for therapeutic potential

Celiac disease (CeD) is an immune-mediated disease, triggered by gluten ingestion, in genetically susceptible individuals. The gluten-free diet (GFD) is the only current treatment for CeD, but is difficult to follow, has high non-adherence rates, and does not always lead to symptomatic or mucosal remission. Microbially-mediated mechanisms have been proposed to contribute to disease pathogenesis, and clinical studies support an association, but mechanistic insight has been difficult to obtain. Recent advances using translational approaches have provided clues to the mechanisms through which bacteria could contribute to CeD pathogenesis. In this review we discuss these bacterially mediated mechanisms, which include the modulation of pathogenic or protective pathways. Targeting these pathways through microbial therapeutics could provide adjuvant therapies to the GFD.

The Role of the Gluten-Free Diet in the Management of Seronegative Enteropathy

The differential diagnosis and treatment of seronegative enteropathy, also termed seronegative villous atrophy (SNVA), is a clinical challenge. Although seronegative coeliac disease (CD) is a frequent cause of SNVA, the aetiology can include immune-mediated, inflammatory, infectious, and drug-related forms. As a misdiagnosis of SNVA can result in patients being unnecessarily placed on a lifelong strict gluten-free diet or even given incorrect immunosuppressive therapy, the aim of this paper is to provide an evidence-based and practical approach for the workup and management of SNVA.

SERONEGATIVE CELIAC DISEASE IN BRAZILIAN PATIENTS: A SERIES OF CASES

BACKGROUND

Celiac disease (CD) is an autoimmune disease characterized by immune reaction mostly to wheat gluten. The diagnosis is based on clinical, serological and histological findings in patients ingesting gluten. Cases that the clinical profile indicates CD and the autoantibodies are negative bring so a dilemma for the professional, as the risk of missed the diagnosis or a delay at the same.

OBJECTIVE

To show the importance of correct diagnosis of cases with seronegative celiac disease (SNCD).

METHODS

Ten cases of SNCD Brazilian patients were retrospectively studied (2013 to 2019). Data of clinical complaints, autoantibodies, IgA serum levels, histological findings and HLA-DQ2/DQ-8 were compiled. Dual-X densitometry, delay at diagnosis, previous autoimmune diseases and family history of CD were also checked.

RESULTS

All SNCD patients presented clinical symptoms of CD, with confirmed diagnosis by histological findings of the duodenal mucosa and HLA-DQ2 and/or HLA-DQ8 positivity. All patients had normal IgA levels and negative autoantibodies (IgA-anti-transglutaminase and anti-endomysial). Dual-X densitometry detected osteopenia in two women and osteoporosis in two males, all with low levels of vitamin D. Delay diagnostic ranged from 1 to 19 years. Familiar occurrence of CD was reported in 40% of the cases. After one year of gluten-free diet, eight patients refer improve of symptoms, while duodenal biopsies, done in five cases, showed histological improvement.

CONCLUSION

Patients who demonstrate the clinical profile of celiac disease with negative serology and normal levels of IgA, especially those who have family members with celiac disease, should be submitted to duodenal biopsies to look for histological findings.

Modern understanding of adult celiac disease

The article presents a modern view of celiac disease within the framework of the classification concept of gluten- associated disorders. The prevalence of the disease, the modern model of the etiopathogenesis of celiac disease, clinical manifestations, and the possibilities of differential diagnosis are discussed. According to the European guidelines, a strategy for monitoring outpatients with celiac disease is presented, based on baseline characteristics of the disease, regular doctor- patient interaction, and prevention of gluten- associated disorders.

TagSNP approach for HLA risk allele genotyping of Saudi celiac disease patients: effectiveness and pitfalls

BACKGROUND

Celiac disease (CD) is a genetically complex autoimmune disease which is triggered by dietary gluten. Human leukocyte antigen (HLA) class II genes are known to act as high-risk markers for CD, where >95% of CD patients carry (HLA), DQ2 and/or DQ8 alleles. Therefore, the present study was conducted to investigate the distribution of HLA haplotypes among Saudi CD patients and healthy controls by using the tag single nucleotide polymorphisms (SNP).

METHODS

HLA-tag SNPs showing strong linkage value (r2>0.99) were used to predict the HLA DQ2 and DQ8 genotypes in 101 Saudi CD patients and in 103 healthy controls by using real-time polymerase chain reaction technique. Genotype calls were further validated by Sanger sequencing method.

RESULTS

A total of 63.7% of CD cases and of 60.2% of controls were predicted to carry HLA-DQ2 and DQ8 heterodimers, either in the homozygous or heterozygous states. The prevalence of DQ8 in our CD patients was predicted to be higher than the patients from other ethnic populations (35.6%). More than 32% of the CD patients were found to be non-carriers of HLA risk haplotypes as predicted by the tag SNPs.

CONCLUSION

The present study highlights that the Caucasian specific HLA-tag SNPs would be of limited value to accurately predict CD specific HLA haplotypes in Saudi population, when compared with the Caucasian groups. Prediction of risk haplotypes by tag SNPs in ethnic groups is a good alternate approach as long as the tag SNPs were identified from the local population genetic variant databases.

Celiac Disease: Fallacies and Facts

Our understanding of the pathophysiology of celiac disease has progressed greatly over the past 25 years; however, some fallacies about the clinical characteristics and management persist. Worldwide epidemiologic data are now available showing that celiac disease is ubiquitous. An elevated body mass index is common at the time of the diagnosis. The gluten-free diet (GFD) is an imperfect treatment for celiac disease; not all individuals show a response. This diet is widely used by people without celiac disease, and symptomatic improvement on a GFD is not sufficient for diagnosis. Finally, the GFD is burdensome, difficult to achieve, and thus has an incomplete efficacy, opening exciting opportunities for novel, nondietary treatments.

The Evolving Landscape of Biomarkers in Celiac Disease: Leading the Way to Clinical Development

Celiac disease is a common immune-mediated disease characterized by abnormal T-cell responses to gluten. For many patients, symptoms and intestinal damage can be controlled by a gluten-free diet, but, for some, this approach is not enough, and celiac disease progresses, with serious medical consequences. Multiple therapies are now under development, increasing the need for biomarkers that allow identification of specific patient populations and monitoring of therapeutic activity and durability. The advantage of identifying biomarkers in celiac disease is that the underlying pathways driving disease are well characterized and the histological, cellular, and serological changes with gluten response have been defined in gluten challenge studies. However, there is room for improvement. Biomarkers that measure histological changes require duodenal biopsies and are invasive. Less invasive peripheral blood cell and cytokine biomarkers are transient and dependent upon gluten challenge. Here, we discuss established biomarkers and new approaches for biomarkers that may overcome current limitations.

AGA Clinical Practice Update on the Evaluation and Management of Seronegative Enteropathies: Expert Review

DESCRIPTION

Our aim was to provide a consensus statement for the best approaches for diagnosis and management of patients with suspected enteropathy, but negative results from serologic tests for celiac disease (seronegative enteropathy).

METHODS

We collected findings from published cohort, case-control, and cross-sectional studies of diagnosis and case series and descriptive studies of management of patients believed to have celiac disease or other enteropathies unrelated to gluten, but negative results from serologic tests. BEST PRACTICE ADVICE 1: Review histologic findings with experienced pathologists who specialize in gastroenterology. BEST PRACTICE ADVICE 2: Serologic tests are essential for an accurate diagnosis of celiac disease. For patients with suspected celiac disease but negative results from serologic tests, total IgA level should be measured; patients should also be tested for anti-tissue transglutaminase, IgA against deamidated gliadin peptide, and endomysial antibody (IgA). Patients with total IgA levels below the lower limit of detection and IgG against tissue transglutaminase or deamidated gliadin peptide, or endomysial antibody, should be considered to have celiac disease with selective IgA deficiency rather than seronegative celiac disease. BEST PRACTICE ADVICE 3: Patients' diets should be carefully reviewed and duodenal biopsies should be collected and analyzed at the time of serologic testing to determine exposure to gluten and accuracy of test results. BEST PRACTICE ADVICE 4: Thorough medication histories should be collected from patients, with attention to angiotensin II receptor blockers, such as olmesartan, along with travel histories to identify potential etiologies of villous atrophy. This will guide additional testing. BEST PRACTICE ADVICE 5: Patients should be analyzed for disease-associated variants in human leukocyte antigen genes; results must be carefully interpreted. Negative results can be used to rule out celiac disease in seronegative patients. BEST PRACTICE ADVICE 6: Patients with suspected celiac disease who are seronegative but have villous atrophy and genetic risk factors for celiac disease must undergo endoscopic evaluation after 1-3 years on a gluten-free diet to evaluate improvements in villous atrophy. A diagnosis of seronegative celiac disease can then be confirmed based on clinical and histologic markers of improvement on the gluten-free diet. BEST PRACTICE ADVICE 7: Seronegative patients with an identified cause for enteropathy should be treated accordingly; a follow-up biopsy might or might not be necessary. BEST PRACTICE ADVICE 8: Patients with persistent signs and symptoms who do not respond to a gluten-free diet, and for whom no etiology of enteropathy is ultimately identified, should be treated with budesonide.

CONCLUSIONS

These best practice guidelines will aid in diagnosis and management of patients with suspected celiac disease, but negative results from serologic tests.

Epidemiology, Presentation, and Diagnosis of Celiac Disease

The incidence of celiac disease is increasing, partly because of improved recognition of, and testing for, the disease. The rise in incidence is also due to a real increase of this immune-based disorder, independent of disease detection. The reasons for this true rise in recent decades are unknown but may be related to environmental factors that may promote loss of tolerance to dietary gluten. Strategies to reduce the development of celiac disease have not been proven successful in randomized trials, but the quantity of early-life gluten exposure has been a major focus of prevention efforts. The criteria for the diagnosis of celiac disease are changing, but in adults, diagnosis still depends on the presence of duodenal villous atrophy while the patient is on a gluten-containing diet, along with findings from serology analysis. Although guidelines in the United States continue to mandate a biopsy at all ages, some children receive a diagnosis of celiac disease without a biopsy. If proven accurate and scalable, assays that detect gluten-HLA tetramer complexes might be used in diagnosis to be made in the context of a gluten-free diet without intestinal biopsy.

The HLA complex and coeliac disease

The Human Leukocyte Antigen (HLA) has a crucial role in the development and pathogenesis of coeliac disease (CD). The genes HLA-DQA1 and HLA-DQB1, both lying in this region and encoding the HLA-DQ heterodimer, are the main genetic predisposing factors to CD. Approximately 90% of CD patients carry the heterodimer HLA-DQ2.5, leaving only a small proportion of patients with lower risk heterodimers (HLA-DQ8, HLA-DQ2.2 or HLA-DQ7.5). These HLA-DQ molecules act as receptors present in the surface of antigen presenting cells and show high affinity for deamidated gluten peptides, which bind and present to CD4⁺ T cells. This triggers the immunological reaction that evolves into CD. Since specific HLA genetics is present in almost the totality of CD patients, HLA typing has a very high negative predictive value, and it can be used to support diagnosis in specific scenarios. HLA risk has been associated to different CD-related features, such as age at onset, clinical outcomes, antibody levels and grade of histological lesion; but further research is needed. HLA-DQ genotypes have been also suggested to modulate the composition of the gut microbiota.

Celiac Disease Screening for High-Risk Groups: Are We Doing It Right?

Celiac disease (CD) is an immune-mediated enteropathy triggered by dietary ingestion of gluten in genetically susceptible patients. CD is often diagnosed by a "case-finding" approach of symptomatic patients. In recent times, the diagnostic paradigm has shifted to investigate patients who may be asymptomatic, but are at high risk of developing CD due to shared genetic susceptibilities. These high-risk groups include first-degree relatives of CD patients and patients with Type 1 diabetes mellitus, autoimmune thyroid disease, Down's syndrome, and Turner syndrome. Moreover, CD is often diagnosed as the cause of iron deficiency anemia or unexplained chronic diarrhea. Although screening for CD with serological tests is not recommended for the general population, it should be considered in these special populations. In this review, we explore screening for CD among high-risk groups in light of recent research and development in the CD arena.