A gene dosage effect of the DQA1*0501/DQB1*0201 allelic combination influences the clinical heterogeneity of celiac disease

Human Leukocyte Antigen-DQ Genotyping in Pediatric Celiac Disease

PURPOSE

The purpose of this study was to determine the pattern of human leukocyte antigen (HLA)-DQ genotype in children diagnosed with celiac disease (CD) (biopsy proven), and to compare this with a control group; and secondarily, to correlate HLA genotypes with clinical profiles of CD.

METHODS

This cross-sectional comparative observational study included 26 controls and 52 patients diagnosed with CD who presented at Sir Padampat Mother and Child Health Institute, Jaipur, from May, 2017 to October, 2018. HLA DQ genotype was assessed for each patients and correlated with clinical profiles.

RESULTS

HLA DQ2/DQ8 genotypes were significantly more common in CD (present in 100.0% cases) than in controls (23.1%) in Northern India (Rajasthan). When HLA DQ2.5 and DQ8 were present together, individuals had significantly more atypical presentations and severe findings on duodenal biopsy. Similarly, patients with the HLA DQ 2.5 genotype were also predisposed to more severe endoscopic findings, while HLA DQ2.2 predisposed them to less severe biopsy findings. HLA DQ8 was significantly associated with later age at diagnosis (>5 years) and shorter stature. The highest HLA DQ relative risk (RR) for CD development was associated with HLA DQ2.5 and DQ2.2 in combination, followed by HLA DQ2.5 and DQ8 in combination, while HLA DQx.5 and HLA DQ2.2 together had the lowest risk.

CONCLUSION

HLA DQ2/DQ8 genotypes are strongly associated with pediatric CD patients in northern India. These genotypes and their combinations may be associated with different clinical presentations of CD, and may help predict severity of CD.

Celiac disease in pediatric patients according to HLA genetic risk classes: a retrospective observational study

BACKGROUND

Celiac disease (CD) is an autoimmune enteropathy in which HLA-DQ haplotypes define susceptibility. Our aim was to evaluate if belonging to a certain HLA-DQ class risk could be associated to the clinical, serological and histological presentation of CD.

METHODS

We performed a retrospective observational monocentric study including all 300 patients diagnosed with CD, who underwent HLA typing. Clinical, serological and histological data was collected from clinical records and their association with HLA-DQ class risk was verified through statistical tests.

RESULTS

In our sample mean age at onset was 6.7 ± 4.2 years, with a prevalence of females (n = 183; 61%), typical symptoms (n = 242; 80.6%) and anti-tTG IgA ≥ 100 U/mL (n = 194; 64.7%). Family history was present only in 19% (n = 57) of patients, and it was not significantly associated with any of the clinical and demographical data analyzed or the belonging to a certain HLA-DQ class risk. We found in the male population more frequently a coexistence of CD and atopic syndrome (males: n = 47; 40.2%; females: n = 50; 27.3%; p = 0.020). Early age of onset, instead, was associated with typical symptoms (m = 6.4 ± 4; p = 0.045) and elevated liver enzymes (m = 5 ± 3.8; p < 0.001), while later age of onset was associated with presence of other autoimmune diseases (m = 8.2 ± 4; p = 0.01). We observed statistically significant influences of HLA class risk on antibodies and liver enzymes levels: G1, G4 and G2 classes showed more frequently anti-tTG IgA ≥ 100 U/mL (n = 44; 80%, n = 16; 69.6%, n = 48; 67.6% respectively; p-value = 0.037), and in patients from G2 class we found enhanced liver enzymes (n = 28; 39.4%; p-value = 0.005). HLA class risk was still significantly associated with anti-tTG ≥ 100 (p = 0.044) and with hypertransaminasemia (p = 0.010) after a multiple logistic regression adjusted for the effect of gender, age at onset and family history.

CONCLUSIONS

We failed to prove an association between HLA-DQ genotypes and the clinical features in our CD pediatric patients. Although, our results suggest an effect of the DQB1-02 allele not only on the level of antibodies to tTG, but possibly also on liver involvement.

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.

Prevalence of coeliac disease in Northwest China: heterogeneity across Northern Silk road ethnic populations

BACKGROUND

Epidemiological data of coeliac disease are lacking from the central Asian region.

AIMS

To verify the occurrence of coeliac disease amongst four major ethnic groups of Xinjiang Uyghur Autonomus Region, China.

METHODS

2277 in-patients with gastrointestinal symptoms (1391 Han, 608 Uyghur, 146 Kazakh and 132 Hui; mean age: 54 ± 12.8 years) were included. Total IgA, anti-deamidated gliadin peptide (DGP)-IgG, and anti-tissue transglutaminase (anti-tTG)-IgA were analysed. All antibody-positive subjects were further tested for endomysial (EMA) antibodies and were HLA genotyped. All subjects with antibody positivity were asked to undergo intestinal biopsy. In addition, a subset of antibody-negative subjects were tested for HLA-DQA1and DQB1.

RESULTS

Among the 2277 subjects, 29 subjects were defined as coeliac disease autoimmune (positive results for anti-tTG IgA and EMA-IgA) (1.27%; 95% confidence interval, 0.81%-1.73%), eight of them underwent biopsy and all showed coeliac disease histology (0.35%; 95% Cl, 0.11%-0.59%). The frequency of coeliac disease autoimmunity was lowest among the Han (0.79%), followed by the Uyghur (1.81%), the Kazakh (2.05%) and the Hui (3.03%). The frequency of the HLA-DQ2 and/or DQ8 haplotype was highest in the Uyghur (52.1%), followed by the Hui (44.4%), the Kazakh (40.0%) and the Han (39.4%). Besides, a three times higher frequency of coeliac disease autoimmunity was found among rural living subjects with significantly higher wheat consumption compared to urban living subjects (3.16% vs 0.97%, P < 0.01).

CONCLUSIONS

In Xinjiang, coeliac disease does occur, especially in the rural area. The HLA haplotype and environment play key roles in the development of coeliac disease.

Carrier frequency of HLA-DQB1*02 allele in patients affected with celiac disease: A systematic review assessing the potential rationale of a targeted allelic genotyping as a first-line screening

BACKGROUND

Celiac Disease (CD) is an immune-mediated disorder, in which the HLA immunogenetic background (DQ2 and DQ8 heterodimers) and environmental trigger (gluten) are well established. Indeed, both factors are necessary – but not sufficient – to develop CD. However, it is very likely that CD is underdiagnosed in both developing and developed countries, due to several aspects, including the fact that a lot of patients present mild and/or atypical symptoms, without the presence of any recognized risk factors. Therefore, the possibility and feasibility of widened screening strategies to identify CD patients are debated.

AIM

To provide further evidence of the main epidemiological importance of HLA-DQB1*02 allele in the population of CD patients.

METHODS

We performed a systematic search in PubMed, EMBASE, Cochrane, Web of Science and Scopus databases, in order to produce a systematic review assessing the carrier frequency of HLA-DQB1*02 allele in the celiac population. Following the PRISMA guidelines, we retrieved all the original articles describing CD patients’ HLA-DQB1 genotype in such a way that could allow to assess the HLA-DQB1*02 carrier frequency among CD patients, along with the evidence of the appropriate diagnostic work-up to achieve a correct and final diagnosis of CD.

RESULTS

The final output of this systematic search in the medical literature consisted of 38 studies providing the appropriate HLA-DQB1 genotype information of the respective CD population. According to this systematic review, including a pool of 4945 HLA-DQ genotyped CD patients, the HLA-DQB1*02 carrier frequency was 94.94%, meaning that only 5.06% of CD patients were completely lacking this allelic variant. Interestingly, if we consider only the studies whereby the prevalence of CD patients affected with type 1 diabetes mellitus was supposed or clearly established to be very low, the frequency of non-HLA-DQB1*02 carriers among CD patients dropped to 3.65%.

CONCLUSION

Such a high carrier frequency of the HLA-DQB1*02 allelic variant (which is > 95%-96% in CD patients without risk factors, like type 1 diabetes mellitus comorbidity) might be exploited to consider a cost-effective and widened screening approach. If a sustainable strategy could be implemented through a low-cost targeted genetic test to detect the individual presence of HLA-DQB1*02 allele, an appropriate algorithm for serological screening in individuals resulting to be genetically predisposed to CD, might be considered.

Celiac disease risk stratification based on HLA-DQ heterodimer (HLA-DQA1 ~ DQB1) typing in a large cohort of adults with suspected celiac disease

BACKGROUNDS

Patients with celiac disease (CeD) carry the major histocompatibility complex class II, HLA-DQ2 or DQ8 haplotype; the absence of these haplotypes excludes a diagnosis of CeD. While the most common and highest risk HLA haplotypes in CeD have been established, the risk profiles of the less common and equivocal HLA haplotypes need further refinement. The aim of this study was to use a large national patient cohort to further stratify the risk gradient of HLA-DQ haplotypes.

METHODS

The study cohort included 24,339 adult patients with suspected CeD and immunoglobulin (Ig)A sufficiency (total IgA ≥ 70 mg/dL) whose samples were assessed at Mayo Clinic Laboratories for HLA-DQ genotyping, total IgA, and tissue transglutaminase (tTG)-IgA. Data from a subset of the patients who had duodenal biopsies were analyzed to determine the risk gradient of CeD. Logistic regression models were used to evaluate the risk gradient and to calculate odds ratios (ORs) for being positive to CeD serology according to different HLA-DQ2 and DQ8 heterodimers.

RESULTS

Of the 24,339 patients, 55% (n = 13,456) expressed HLA-DQ2 or DQ8 heterodimers. Compared with patients who had non-permissive HLA-DQ heterodimers, patients who had HLA-DQ2 homozygosity (HLA-DQ2.5/DQ2.5, HLA-DQ2.5/DQ2.2, or HLA-DQ2.2/DQ2.2) showed increased odds for tTG-IgA positivity (OR = 96.9; 95% CI, 58.3-147.9). Interestingly, the odds for patients who were compound heterozygous for HLA-DQ2.5 and HLA-DQ8 were similar to those for HLA-DQ2.5 heterozygotes. However, a single HLA-DQ2.2 haplotype (without HLA-DQ8, DQ2.2 heterozygous) was not associated with tTG-IgA positivity. These findings were confirmed in a subset of patients (n = 738) who had duodenal biopsies performed in addition to CeD serologic testing.

DISCUSSION

This large national reference laboratory cohort study demonstrated that HLA-DQ2.2 heterozygous is not associated with positive tTG-IgA serology, suggesting the reclassification of this haplotype as non-permissive for CeD.

Is the double gene dose of DQ2.5 or DQ2.5/DQ2.2 an involved factor in the clinical features of celiac disease?

Objectives: Celiac disease (CD) is barely known if the quantitative effect of DQB1*02 (DQ2) double dose in antigen presentation to T-cells has translation into the clinic. For this, we have conducted a case-control study in a cohort of two hundred and nineteen patients with CD. Material and methods: For the control group, individuals were enrolled with single dose of DQ2, carrying DQ2.5 heterodimers in heterozygous state (n = 109). The cases with CD were diving into three groups: cases with overall DQ2 double dose (n = 110), DQ2.5 homozygous (n = 33) and DQ2.5/DQ2.2 heterozygous (n = 77). Prevalence and associations of demographic, laboratory, histological and clinical characteristics between the control group and cases were studied. Results: No differences were found for the total of 16 variables analyzed between the control group and overall DQ2 double dose as well as DQ2.5 homozygous cases. In contrast to DQ2.5/DQ2.2, heterozygous cases presented a protection factor for developing allergy to airway allergens regarding the control group (OR = 0.210, p = .019). Conclusions: To date, this negative association has not been described. Further studies will be necessary to elucidate the implication of this protection factor in CD. Since, until now the association between CD and allergic diseases has been poorly studied.

Prevalence of Celiac Disease in a Long-term Study of a Spanish At-genetic-risk Cohort From the General Population

OBJECTIVES

To perform long-term celiac disease (CD) screening in an HLA-DQ2 (+) cohort from the general population and to assess the influence of risk genotypes on its development.

METHODS

In 2004, an HLA-DQ2 (+) cohort was selected. After the first CD screening at age 2 to 3 years, we performed a follow-up screening 8 to 10 years later. Antitransglutaminase 2 antibodies were determined using a rapid test kit. Results were confirmed by serum IgA antitransglutaminase 2 and IgA endomysial antibody determination. CD diagnosis was carried out by intestinal biopsies. Four HLA-DQ2 genotypic groups were used: G1: DQ2.5/DQ2.5 (G1A) or DQ2.5/ DQ2.2 (G1B); G2: DQ2.2/DQ7.5 (DQ2.5 trans); G3: DQ2.5/ X; G4: DQ2.2/X.

RESULTS

CD prevalence after 10 years of follow-up was 5.8% (95% confidence interval 3.8-8.7). One of every 3 HLA-DQ2(+) children carried at least 1 haplotype DQ2.2 or DQ7. The homozygous genotype DQ2.5/DQ2.5 and the HLA-DQ2.5 trans genotype increased CD risk 4- and 3-fold, respectively. The homozygous genotype DQ2.5/ DQ2.2 did not increase the CD risk. Children carrying G1 or G2 genotypes were diagnosed with CD earlier and more frequently during the follow-up compare with those carrying G3 or G4 genotypes. Approximately 81% of children with spontaneous antibody negativization after the first screening maintained negative antibodies.

CONCLUSIONS

A repeated screening of at-risk children during their follow-up allowed us to diagnose new CD cases. In our cohort, HLA- DQ2.5 trans genotype conferred a higher risk in the development of CD than HLA- DQ2.5/DQ2.2. The majority of children with potential CD and CD autoimmunity at 10 years of age remained healthy.

HLA-DQ2 homozygosis increases tTGA levels at diagnosis but does not influence the clinical phenotype of coeliac disease: A multicentre study

BACKGROUND AND PURPOSE

Magnitude of gluten-specific T-cell responses in coeliac disease (CD) might be dependent on HLA-DQ2 gene dose. We aimed to investigate the effects of HLA-DQB1*02 allele dose on clinical outcomes.

METHODS

We reviewed the charts of all coeliac patients attending to three Hungarian university clinics after 1997 and included those patients, who (a) were diagnosed with CD, (b) underwent high-resolution HLA typing and (c) were ≥18 years at the time of data collection. HLA typing was performed to determine DQB1*02 allele dose. Patients were divided into risk groups by DQB1*02 allele dose, as follows: high-, intermediate- and low-risk groups corresponded to a double, single and zero doses, respectively. We used ANOVA and Pearson's chi-squared test to explore association between HLA risk and clinical variables.

RESULTS

A total of 727 coeliac patients attended the clinics but only 105 (14.4%) patients were eligible for inclusion. High, intermediate and low HLA risk patients comprised 35.3%, 52.3% and 12.3% of the study population, respectively. Double dose of HLA-DQB1*02 was more frequent in patient with high tTGA level (>10 times the upper limit of normal; p = 0.045). Gene dose was not associated with younger age at diagnosis (p = 0.549), gender (p = 0.739), more severe diagnostic histology (p = 0.318), more frequent classical presentation (p = 0.846), anaemia (p = 0.611), metabolic bone disease (p = 0.374), dermatitis herpetiformis (p = 0.381) and autoimmune diseases (p = 0.837).

CONCLUSIONS

Our study shows a significant gene dose effect in terms of tTGA level at diagnosis, but no significant association between HLA-DQB1*02 allele dose and the clinical outcomes in CD.

Classical celiac disease is more frequent with a double dose of HLA-DQB1*02: A systematic review with meta-analysis

Background and aims

Experimental data suggest that the HLA-DQ2 gene dose has a strong quantitative effect on clinical outcomes and severity of celiac disease (CD). We aimed to conduct a meta-analysis with systematic review to investigate the association between HLA-DQB1*02 gene doses and the characteristics of CD.

Methods

We searched seven medical databases for studies discussing HLA-DQB1 gene dose in CD and various disease characteristics, such as clinical presentation, histology, age at diagnosis, and comorbidities. Odds ratios (OR, for categorical variables) and weighted mean differences (for age) were calculated to compare patients with a double dose of HLA-DQB1*02 versus those with single and zero doses. Heterogeneity was tested with I²-statistics and explored by study subgroups (children and adults).

Results

Twenty-four publications were eligible for meta-analysis. Classical CD was more frequent with a double versus single dose of the HLA-DQB1*02 allele (OR = 1.758, 95%CI: 1.148–2.692, I² = 0.0%). In pediatric studies, gene dose effect was more prominent (OR = 2.082, 95%CI: 1.189–3.646, I² = 0.0% and OR = 3.139, 95%CI: 1.142–8.630, I² = 0.0% for the comparisons of double versus single and double versus zero dose, respectively). Atrophic histology was more prevalent with a double versus zero dose (OR = 2.626, CI: 1.060–6.505, I² = 21.3%). We observed no gene dose effect regarding diarrhea, age at diagnosis, the severity of villous atrophy, and the association with type 1 diabetes mellitus.

Conclusion

A double dose of HLA-DQB1*02 gene seems to predispose patients to developing classical CD and villous atrophy. Risk stratification by HLA-DQB1*02 gene dose requires further clarification due to the limited available evidence.

HLA-DQ2 and -DQ8 genotype frequency in Syrian celiac disease children: HLA-DQ relative risks evaluation

Background

Celiac disease (CD) is a common autoimmune disease in Syria which manifesting with inflammation of the small intestine and with various extra intestinal symptoms. The disease is associated with human HLA-DQ genes encoding HLA-DQ2 and DQ8 proteins.

Methods

In this study, 49 children patients of CD and 58 healthy control samples were genotyped for HLA-DQ genes using SSP-PCR technique. Relative risks for different genotypes were also evaluated.

Results

The DQB1*0201 allele was the most common in the patients (77.6%) followed by DQB1*0302 allele (10.2%). The highest HLA-DQB risk for CD development was found in patients carriers a DQ2.5/DQ8 genotype (1/10), followed by the patients carriers DQ2.5/DQ2.5 (1/12).

Conclusion

The significant differences in the frequency of HLA-DQ2 and HLA-DQ8 in Syrian patients in compared with controls and relative risks predicted demonstrated the importance role of these alleles in the development of CD in Syrian children patients.

HLA-DQ genetics in children with celiac disease: a meta-analysis suggesting a two-step genetic screening procedure starting with HLA-DQ β chains

BackgroundSpecific HLA-DQ genes have been recognized as necessary - but not sufficient - factors for the occurrence of Celiac Disease (CD). Through a meta-analysis, evaluating the distribution of CD-related HLA genotypes in children, we aimed at providing insights for a potential widened screening strategy.MethodsAfter a systematic search on the association between class II HLA genes and CD in children, 46 publications were obtained and assessed for eligibility. A total of 13 eligible studies were submitted to data extraction and analysis (10 case-control studies and 3 cohort studies). Case-control studies collectively enrolled 740 CD patients and 943 controls.ResultsIn the population-stratified analysis, the following alleles conferred a significantly increased risk for CD: HLA-DQB1*02 (odds ratio [OR]=10.28) and HLA-DQB1*03:02 (OR=2.24). By drafting a risk gradient to develop CD according to HLA genetic background, the highest risk is confirmed to exist for DQ2/DQ2 homozygous subjects, regardless of the ethnicities (OR=5.4). Actually, the genotype DQ2/β2 showed basically the same risk (OR=5.3). Indeed, no differences have been found in CD risk between DQ2/β2 and DQ2/DQ2, as well as between DQ8/β2 and DQ2/DQ8, and between β2/DQX and DQ2/X.ConclusionThe HLA-DQB1*02:01 allele is present in more than 90% CD children. In the perspective of a widened pediatric population screening for CD, a double-step process might be suggested: HLA-DQB1*02:01 might be investigated first and, only if this result is positive, children might be candidate for a prospective serologic screening, as a second step.

DQ2, DQ7 and DQ8 Distribution and Clinical Manifestations in Celiac Cases and Their First-Degree Relatives

HLA-linked genes are relevant to celiac disease (CD); the potential genetic differences present worldwide are not fully understood. Previous results suggest that the distribution of HLA-DQ2/DQ7/DQ8 in Chile may differ from that in Europe and North America. In celiac patients and their first-degree relatives (FDRS), we assessed their clinical, serological and histological characteristics, determined HLA-DQ2, HLA-DQ7 and HLA-DQ8 alleles and genotypes, and evaluated the relations between them. A total of 222 individuals were assessed (56 cases, 166 FDRs). 16.9% of FDRs were tTG positive; 53.6% of them showed overweight/obesity and 3% undernourishment; they spontaneously declared being asymptomatic, but detailed questioning revealed that 60.7% experienced symptoms, which had not been investigated. DQ2 was present in 53.9% and 43.9.0% of cases and FDRs (p < 0.05). The most frequent genotype distribution was DQ2/DQ7 (fr 0.392 (cases) and 0.248 (FDRs), respectively, p < 0.02). The next most common genotypes were HLA-DQ2/DQ8 (fr 0.236 in FDRs and 0.176 in cases, p < 0.05). 3.92% cases were not HLA-DQ2/DQ8 carriers. Among tTG positive FDRs, 57.4%, 22.3% and 20.2% carried DQ2, DQ7 and DQ8, respectively. In cases, 72.7% of the biopsies classified Marsh ≥ 3 carried at least one DQ2; 91.7% of DQ2/DQ2 and 88.3% of DQ2/DQ7 were Marsh ≥ 3. Thus, DQ2 frequency is lower than reported; the higher frequency found for DQ8 and DQ7 concur with recent publications from Argentine and Brazil. These results suggest that although CD may manifest clinically in ways similar to those described in other populations, some genetic peculiarities in this region deserve further study.

Clinical features of celiac disease: a prospective birth cohort

OBJECTIVES

To investigate clinical features of celiac disease (CD) and their association with risk factors for CD in a genetic risk birth cohort.

METHODS

Children from 6 clinical centers in 4 countries positive for HLA-DR3-DQ2 or DR4-DQ8 were annually screened for tissue transglutaminase antibodies (tTGA) and assessed for symptoms by questionnaires. Associations of symptoms with anthropometrics, known risk factors for CD, tTGA levels, and mucosal lesions in those biopsied were examined.

RESULTS

Of 6706 screened children, 914 developed persistent positive tTGA, 406 underwent biopsies, and 340 had CD. Compared with age-matched tTGA-negative children, those with persistent tTGA were more likely to have symptoms at 2 (34% vs 19%, P < .001) and 3 years of age (28% vs 19%, P = .009) but not at 4 years (27% vs 21%, NS). Z-scores for height, weight, and BMI did not differ between groups. In children with persistent tTGA, having ≥ 1 symptom was associated with family history of CD (odds ratio = 2.59, 95% confidence interval, 1.21-5.57) but not with age, gender, or HLA-DR3-DQ2 homozygosity. At seroconversion, tTGA levels were higher in symptomatic than asymptomatic children (P < .001), in those from CD families (P < .001), and in US participants (P < .001) but not associated with age, gender, or HLA genotype. tTGA levels correlated with severity of mucosal lesions both in symptomatic (r = 0.53, P < .001) and asymptomatic children (r = 0.22, P = .01).

CONCLUSIONS

A majority of children detected with persistent tTGA in screenings are asymptomatic and have normal growth by age 4 years. tTGA levels correlate more strongly with severity of mucosal lesions in symptomatic as compared with asymptomatic children.

Allele and haplotype frequencies for HLA-DQ in Iranian celiac disease patients

AIM: To assess the distribution of human leukocyte antigen (HLA)-DQ2 and -DQ8 in Iranian celiac disease (CD) patients and compare them to healthy Iranian controls.

METHODS: To predict the HLA-DQA1 and -DQB1 genes, we used six previously reported HLA-tagging single nucleotide polymorphism to determine HLA genotypes in 59 Iranian patients with ‘biopsy-confirmed’ CD and in 151 healthy Iranian individuals. To test the transferability of the method, 50 cases and controls were also typed using a commercial kit that identifies individual carriers of DQ2, DQ7 and DQ8 alleles.

RESULTS: In this pilot study 97% of CD cases (n = 57) and 58% of controls (n = 87) were carriers of HLA-DQ2 and/or HLA-DQ8 heterodimers, either in the homozygous or heterozygous state. The HLA-DQ pattern of these 57 CD patients: heterozygous DQ2.2 (n = 14) and homozygous DQ2.2 (n = 1), heterozygous DQ2.5 (n = 33) and homozygous DQ2.5 (n = 8), heterozygous DQ8 (n = 13) and homozygous DQ8 (n = 2). Two CD patients were negative for both DQ2 and DQ8 (3%).

CONCLUSION: The prevalence of DQ8 in our CD population was higher than that reported in other populations (25.4%). As reported in other populations, our results underline the primary importance of HLA-DQ alleles in the Iranian population’s susceptibility to CD.

Improving coeliac disease risk prediction by testing non-HLA variants additional to HLA variants

BACKGROUND

The majority of coeliac disease (CD) patients are not being properly diagnosed and therefore remain untreated, leading to a greater risk of developing CD-associated complications. The major genetic risk heterodimer, HLA-DQ2 and DQ8, is already used clinically to help exclude disease. However, approximately 40% of the population carry these alleles and the majority never develop CD.

OBJECTIVE

We explored whether CD risk prediction can be improved by adding non-HLA-susceptible variants to common HLA testing.

DESIGN

We developed an average weighted genetic risk score with 10, 26 and 57 single nucleotide polymorphisms (SNP) in 2675 cases and 2815 controls and assessed the improvement in risk prediction provided by the non-HLA SNP. Moreover, we assessed the transferability of the genetic risk model with 26 non-HLA variants to a nested case-control population (n=1709) and a prospective cohort (n=1245) and then tested how well this model predicted CD outcome for 985 independent individuals.

RESULTS

Adding 57 non-HLA variants to HLA testing showed a statistically significant improvement compared to scores from models based on HLA only, HLA plus 10 SNP and HLA plus 26 SNP. With 57 non-HLA variants, the area under the receiver operator characteristic curve reached 0.854 compared to 0.823 for HLA only, and 11.1% of individuals were reclassified to a more accurate risk group. We show that the risk model with HLA plus 26 SNP is useful in independent populations.

CONCLUSIONS

Predicting risk with 57 additional non-HLA variants improved the identification of potential CD patients. This demonstrates a possible role for combined HLA and non-HLA genetic testing in diagnostic work for CD.

Late diagnosis of celiac disease in an asymptomatic infant with growth failure

The clinical spectrum for celiac disease (CD) is broad and includes cases with either typical (intestinal) or atypical (extraintestinal) features, often making the diagnosis of CD very difficult.

We describe the case of a girl presenting with stunted growth and malnourishment. She was evaluated at 14 months for decreased growth rate without any signs of gastrointestinal, renal or endocrine disorders. She was evaluated for CD, but resulted negative for anti-tTG antibodies.

At the age of 4.1 years, she exhibited basal dental enamel hypoplasia, iron deficiency anaemia despite repeated iron supplementation, with persistent reduced height (-2.79 SDS), BMI (-0.76 SDS), growth velocity (-1.79 SDS) and delayed bone age (1.5 year). The CD screening was repeated and very high anti-tTG-IgA (128 IU/ml, normal values < 7 IU/ml) and anti-tTG-IgG (77 IU/ml, normal values < 7 IU/ml) values were found. HLA genotyping revealed an HLA DQ2 haplotype. A duodenal biopsy revealed severe villous atrophy with crypt hyperplasia and increased intraepithelial lymphocytes (> 40 IELs/100 epithelial cells) confirming the diagnosis of CD. A gluten-free diet was started and after only four months, her growth velocity increased from 4.83 cm/year (-1.79 SDS) to 6.53 cm/year (-0.15 SDS).

In conclusion, we report the development of a positive serology for CD in an asymptomatic child with growth retardation, who previously was investigated for CD and resulted negative. Therefore, when faced with retarded growth in young patients, after excluding other malabsorption conditions and even when CD serological markers are negative, the paediatric endocrinologist should request HLA genotyping, before the intestinal biopsy, in order to check for the presence of risk alleles.

Pediatric and adult celiac disease: similarities and differences

Differences between children and adults in celiac disease (CD) presentation and epidemiology are reviewed here. Clinical manifestations, histological changes, serology, and response to gluten-free diet are similar. Differences exist in epidemiology, type of clinical presentations, coexisting diseases, complications, and association with obesity. CD is two to five times more common in children than in adults. Classical CD with gastrointestinal symptoms is more common in children whereas nonclassical CD dominates in adults. A gene dose phenomenon (double-dose HLA-DQB1 02 allele) is postulated to be responsible for this difference. Coexisting autoimmune diseases like diabetes mellitus type 1, Sjogren's syndrome, and dermatitis herpetiformis are more common in adults than in children (42 % vs. 5 %). The association of overweight/obesity and CD is stronger in adults than in children (22.5 % vs. 14 %). Besides poor compliance, pancreatic insufficiency, bacterial overgrowth, lactose intolerance, irritable bowel syndrome, lymphocytic colitis, and microscopic colitis are considered responsible for nonresponsive CD in adults but not in children. Complications like refractory sprue and small intestinal neoplasms are seen exclusively in adults. Existing diagnostic criteria (modified ESPGHAN) are not suitable for diagnosing CD in adults as the majority of cases are either nonclassical or subclinical CD.

Molecular diagnosis of celiac disease: are we there yet?

BACKGROUND

Celiac disease (CD) is a complex genetic disorder of the small intestine resulting from aberrant cellular responses to gluten peptides. It may affect as much as 1% of the Western population and the only treatment is a lifelong gluten-free diet. Allelic variants of the HLA-DQ locus, coding for the HLA-DQ2 and HLA-DQ8 molecules, contribute to ∼ 40% of CD etiology, whereas other genes, such as MYO9B, CTLA4, IL2, IL21, PARD3 and MAGI2, have only a modest effect. Most of these genes have shown varied association among different populations and an overlap with other autoimmune or inflammatory disorders, indicating that such disorders may share common pathways.

OBJECTIVES

In this review, a molecular approach into diagnostics of celiac disease is shown.

CONCLUSIONS

Genome-wide association studies will allow more genes to be identified, and knowing how risk variants combine will help to predict better the risk for the individual. HLA typing can already be used to identify high-risk individuals.

Pathophysiology of celiac disease

Celiac disease results from the interplay of genetic, environmental, and immunologic factors. An understanding of the pathophysiology of celiac disease, in which the trigger (wheat, rye, and barley) is known, will undoubtedly reveal basic mechanisms that underlie other autoimmune diseases (eg, type 1 diabetes) that share many common pathogenic perturbations. This review describes seminal findings in each of the 3 domains of the pathogenesis of celiac disease, namely genetics, environmental triggers, and immune dysregulation, with a focus on newer areas of investigation such as non-HLA genetic variants, the intestinal microbiome, and the role of the innate immune system.

Celiac disease in children and adolescents: special considerations

Although there are many commonalities between adult and pediatric celiac disease (CD), special considerations must be taken into account when working with children and adolescents. In this patient population, there are unique aspects of the epidemiology, pathogenesis, presentation, diagnosis, and management of CD. In terms of management, early and timely recognition of CD can maximize childhood and adolescent development and prevent complications. This requires insight into the unique presentations of CD in the pediatric population. Furthermore, health care providers must use proper screening methods and continue surveillance of at-risk individuals throughout childhood. Potential interventions for primary prevention of CD in children, although not completely understood, may offer some benefit. The goals of this article are to discuss in detail these special considerations when dealing with pediatric CD.

HLA-DRB1-DQB1 haplotypes confer susceptibility and resistance to multiple sclerosis in Sardinia

Introduction

Genetic predisposition to multiple sclerosis (MS) in Sardinia (Italy) has been associated with five DRB1*-DQB1* haplotypes of the human leukocyte antigen (HLA). Given the complexity of these associations, an in-depth re-analysis was performed with the specific aims of confirming the haplotype associations; establishing the independence of the associated haplotypes; and assessing patients' genotypic risk of developing MS.

Methods and Results

A transmission disequilibrium test (TDT) of the DRB1*-DQB1* haplotypes in 943 trio families, confirmed a higher than expected transmission rate (over-transmission) of the *13:03-*03:01 (OR = 2.9, P = 7.6×10⁻³), *04:05-*03:01 (OR = 2.4, P = 4.4×10⁻⁶) and *03:01-*02:01 (OR = 2.1, P = 1.0×10⁻¹⁵) haplotype. In contrast, the *16:01-*05:02 (OR = 0.5, P = 5.4×10⁻¹¹) and the *15:02-*06:01 (OR = 0.3, P = 1.5×10⁻³) haplotypes exhibited a lower than expected transmission rate (under-transmission). The independence of the transmission of each positively and negatively associated haplotype was confirmed relative to all positively associated haplotypes, and to the negatively associated *16:01-*05:02 haplotype. In patients, carriage of two predisposing haplotypes, or of protective haplotypes, respectively increased or decreased the patient's risk of developing MS. The risk of MS followed a multiplicative model of genotypes, which was, in order of decreasing ORs: *04:05-*0301/*03:01-*02:01 (OR = 4.5); *03:01-*02:01/*03:01-*02:01 (OR = 4.1); and the *16:01-*05:02/*16:01-*0502 (OR = 0.2) genotypes. Analysis of DRB1 and DQB1 protein chain residues showed that the Val/Gly residue at position 86 of the DRB1 chain was the only difference between the protective *16:01- *15:02 alleles and the predisposing *15:01 one. Similarly, the Ala/Val residue at position 38 of the DQB1 chain differentiated the positively associated *06:02 allele and the negatively associated *05:02, *06:01 alleles.

Conclusions

These findings show that the association of specific, independent DRB1*-DQB1* haplotypes confers susceptibility or resistance to MS in the MS-prone Sardinian population. The data also supports a functional role for specific residues of the DRB1 and DQB1 proteins in predisposing patients to MS.

HLA-DQ types of celiac disease in Libyan children with type 1 diabetes mellitus

OBJECTIVE

To determine the genetic profile of celiac disease (CD) in Libyan children with type 1 diabetes as there are no data on the frequency of human leukocyte antigen (HLA)-related CD-predisposing genes in diabetic patients in Libya.

METHODS

We randomly studied 218 Libyan type 1 diabetic children. The mean age was 12.2±4.6 years; 56% were female patients. The mean duration of diabetes was 4.7±4.0 years. All patients were screened for CD with IgA tissue-transglutaminase (tTG) and endomysium antibodies. Patients with positive immunological screen were programmed for a small-bowel biopsy. HLA-DRB1* and HLA-DQB1* were genotyped in all tTG-positive patients.

RESULTS

Twenty-seven (12.4%) out of 218 patients with type1 diabetes had positive tTG, and 20 (9.2%) of these patients were positive for endomysium antibodies. Five patients (5/27) were already known cases of biopsy-proven CD. Biopsy was not performed in two patients. One biopsy result was normal, whereas 19 biopsies demonstrated morphological changes consistent with CD. Forty-eight percent of the anti-tTG-positive group were homozygous for HLA-DQ2, whereas 75% of biopsy-proven CD patients had HLA-DQ2, 21% had HLA-DQ2/DQ8, and 4% had HLA-DQ8. In addition, the majority (70%) carried HLA-DQ2 linkage with HLA-DRB1*03.

CONCLUSION

Overall, biopsy-confirmed prevalence of CD was 11% (24 of 218). The present study confirms that CD in the Libyan type 1 diabetic population is high when compared with European and US studies, and for the first time we document that this population shares similar HLA-DQ2 genotype. This supports the theory regarding the role of the environment as an important factor in CD development in this part of the world.

European Society for Pediatric Gastroenterology, Hepatology, and Nutrition guidelines for the diagnosis of coeliac disease

OBJECTIVE

Diagnostic criteria for coeliac disease (CD) from the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) were published in 1990. Since then, the autoantigen in CD, tissue transglutaminase, has been identified; the perception of CD has changed from that of a rather uncommon enteropathy to a common multiorgan disease strongly dependent on the haplotypes human leukocyte antigen (HLA)-DQ2 and HLA-DQ8; and CD-specific antibody tests have improved.

METHODS

A panel of 17 experts defined CD and developed new diagnostic criteria based on the Delphi process. Two groups of patients were defined with different diagnostic approaches to diagnose CD: children with symptoms suggestive of CD (group 1) and asymptomatic children at increased risk for CD (group 2). The 2004 National Institutes of Health/Agency for Healthcare Research and Quality report and a systematic literature search on antibody tests for CD in paediatric patients covering the years 2004 to 2009 was the basis for the evidence-based recommendations on CD-specific antibody testing.

RESULTS

In group 1, the diagnosis of CD is based on symptoms, positive serology, and histology that is consistent with CD. If immunoglobulin A anti-tissue transglutaminase type 2 antibody titers are high (>10 times the upper limit of normal), then the option is to diagnose CD without duodenal biopsies by applying a strict protocol with further laboratory tests. In group 2, the diagnosis of CD is based on positive serology and histology. HLA-DQ2 and HLA-DQ8 testing is valuable because CD is unlikely if both haplotypes are negative.

CONCLUSIONS

The aim of the new guidelines was to achieve a high diagnostic accuracy and to reduce the burden for patients and their families. The performance of these guidelines in clinical practice should be evaluated prospectively.

Concomitant autoimmunity in myasthenia gravis--lack of association with IgA deficiency

A marked increase in concomitant autoimmune diseases has previously been noted in patients with myasthenia gravis (MG). We show that these diseases occur both before and after the onset of MG and that the process is not influenced by thymectomy. IgA deficiency (IgAD), which is strongly associated with the same HLA haplotype as early onset MG, has recently been suggested to be an autoimmune disease. However, there was no increase in the prevalence of IgAD in a large cohort of Swedish MG patients.

Gluten-dependent enteropathy and atypical human leukocyte antigen alleles

The risk for developing celiac disease is associated with the major histocompatibility complex class II human leukocyte antigen DQ2 and DQ8. We retrospectively reviewed the medical records of 127 consecutive cases of adult-onset celiac disease evaluated at a single United States center to determine the distribution of the associated human leukocyte antigen DQA1 and DQB1 alleles. The median patient age of diagnosis was 41 (range, 16-81) years. Ninety-five adults underwent human leukocyte antigen DQ typing. Eighty patients were DQ2 positive, 24 were DQ8 positive, and 11 were DQ2 and DQ8 positive. Four patients carried the uncommon, low-risk haplotype DQ2.2 (DQA1*02 and DQB1*02) without DQA1*05. Two patients did not carry human leukocyte antigen DQ2 or DQ8. All of the patients with atypical human leukocyte antigen DQ responded to a gluten-free diet. Although the majority of patients carry the human leukocyte antigen DQ2 or DQ8, gluten-dependent enteropathy periodically presents in adults with low-risk alleles.

The CD45 77C/G allele is not associated with myasthenia gravis - a reassessment of the potential role of CD45 in autoimmunity

Background

The G allele of the CD45 77C/G SNP (rs17612648), which has previously been suggested to be associated with autoimmune disorders, was genotyped in 446 Swedish myasthenia gravis (MG) patients and 2303 matched controls.

Results

There was no association between the polymorphism and patient group as a whole (p = 0.199), nor with clinical subgroups. Our results add to a growing number of studies unable to find association between the 77C/G polymorphism and autoimmune disorders. One control sample, from an adult blood donor, was homozygous for the G allele, yet negative for a panel of auto-antibodies, representing the first homozygous individual studied in this respect.

Conclusions

The 77C/G mutation does not predispose to MG, and its role in autoimmunity may have to be re-evaluated.

Contribution of histological, serological, and genetic factors to the clinical heterogeneity of adult-onset coeliac disease

OBJECTIVE

Although the factors predisposing to coeliac disease (CD) are largely understood, it remains unclear what determines the clinical heterogeneity of the disease. The aim of this study was to explore the contribution of histological, serological, and genetic factors to disease presentation.

MATERIAL AND METHODS

The study was designed as a retrospective chart review of 384 unrelated Caucasian patients diagnosed with CD after the age of 16 at a single UK centre.

RESULTS

We found that 8.8% of IgA-competent CD patients were endomysial antibody (EMA)-negative. Compared with the EMA-positive group, EMA-negative CD patients had a lower prevalence of iron deficiency (52.0% versus 72.6%, p=0.03) and Marsh IIIb-c lesions (66.7% versus 85.3%, p=0.03). Histological severity at diagnosis correlated with anaemia (p<0.01), folate deficiency (p<0.01), and iron deficiency (p=0.05), but no other laboratory or clinical features. Compared with human leucocyte antigen (HLA)-DQ2.5-positive patients, those carrying HLA-DQ2.2 were similar in terms of all the characteristics we considered, whereas those carrying HLA-DQ8 had a lower frequency of EMA positivity (62.5% versus 92.6%, p<0.01). The proportion of EMA-positive patients increased with frequency of the HLA-DQB1*0201 allele (76.7% versus 92.3% versus 96.4% for 0 versus 1 versus 2 alleles, p<0.01); no other evidence of a gene-dose effect of HLA-DQB1*0201 was observed.

CONCLUSIONS

Histological severity at diagnosis of CD is associated with anaemia and some micronutrient deficiencies, but no other clinical features. The proportion of EMA-positive patients is higher amongst those carrying HLA-DQ2 than in those carrying HLA-DQ8, and is highest in HLA-DQ2 homozygotes. We found no correlation between frequency of the HLA-DQ alleles encoding HLA-DQ2.5 and CD severity.

Analysis of HLA and non-HLA alleles can identify individuals at high risk for celiac disease

BACKGROUND & AIMS

Celiac disease (CD) is a common chronic disorder of the small intestine, resulting from aberrant cellular responses to gluten peptides, and often remains undiagnosed. It is a complex genetic disorder, although 95% of the patients carry the risk heterodimer human leukocyte antigen (HLA)-DQ2. Genome-wide association studies on CD have identified 9 non-HLA loci that also contribute to CD risk, most of which are shared with other immune-related diseases. Our aim is to predict the genetic risk for CD using HLA and non-HLA risk alleles.

METHODS

We selected 10 independent polymorphisms in 2,308 cases and 4,585 controls from Dutch, UK, and Irish populations and categorized the individuals into 3 risk groups, based on their HLA-DQ2 genotype. We used the summed number of non-HLA risk alleles per individual to analyze their cumulative effect on CD risk, adjusting for gender and population group in logistic regression analysis. We validated our findings in 436 Italian cases and 532 controls.

RESULTS

CD cases carried more non-HLA risk alleles than controls: individuals carrying > or = 13 risk alleles had a higher CD risk (odds ratio, 6.2; 95% confidence interval, 4.1-9.3) compared with those carrying 0-5 risk alleles. Combining HLA and non-HLA risk genotypes in one model increases sensitivity by 6.2% compared with using only HLA for identification of high-risk individuals with slight decrease in specificity.

CONCLUSIONS

We can use non-HLA risk factors for CD to improve identification of high-risk individuals. Our risk model is a first step toward better diagnosis and prognosis in high-risk families and population-based screening.

Phenotypic variance in childhood coeliac disease and the HLA-DQ/DR dose effect

OBJECTIVE

Coeliac disease (CD) is associated with HLA-DQ2 and DQ8. The clinical picture is variable and certain human leucocyte antigen (HLA) DQ/DR combinations have a higher relative risk (RR) for CD than others. Moreover, the HLA-DQ gene-dose effect has an impact on the strength of the gluten-specific T-cell response and thus may correlate with clinical presentation and severity of CD. The aim of this study was to determine the correlation between HLA-DQ/DR-based genotypes and the variation in phenotypes of the disease.

MATERIAL AND METHODS

A total of 113 non-related Caucasian children clinically diagnosed with CD during the period 1980-2003 with a known HLA type were included in the study. Patients were divided into four categories according to amount of disease expression predisposing to HLA-DQ2 or HLA-DQ8 molecules and the known RR of their HLA-DR/DQ type for CD: high (DR3DQ2 homozygous and DR3DQ2/DR7DQ2), substantial (DR3DQ2/DR5DQ7 and DR5DQ7/DR7DQ2), moderate (DR3DQ2-DR4DQ8 and DR3DQ2/DR*DQ*) and low (DR7DQ2/DR*DQ*, DR4DQ8- DR*DQ* and DR*DQ*- DR*DQ*). The clinical data and HLA genotypes of these patients were compared.

RESULTS

The 113 children were diagnosed with CD at a mean age of 4.6 years and boys were significantly older than girls when diagnosed (p=0.01). RR for having CD was highest for the high HLA-risk group (RR 8.1). With the exception of a greater frequency of abdominal distension and fewer non-gastrointestinal symptoms in the substantial HLA-risk group, there were no significant differences in clinical characteristics or degree of severity of the small-bowel histological findings between the children in the different HLA-risk groups.

CONCLUSION

No correlation was found between disease severity and a double HLA-DQ2 gene dose.

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.

HLA-DQB1*02 dose effect on RIA anti-tissue transglutaminase autoantibody levels and clinicopathological expressivity of celiac disease

OBJECTIVES

Celiac disease is an autoimmune enteropathy caused by gluten ingestion in genetically susceptible individuals. Anti-transglutaminase autoantibody (tTGAb) assay is useful to detect candidates undergoing intestinal biopsy. Our aim was to investigate whether the DQB1*02 allele could influence tTGAb titers and the clinicopathological expressivity of the disease.

METHODS

A total of 124 patients with celiac disease, tested for RIA tTGAb at diagnosis, were typed for HLA-DRB1, -DQA1, and -DQB1 genes and divided according to the number of DQB1*02 alleles: group 1, homozygous; group 2, heterozygous; group 3, negative.

RESULTS

The mean of tTGAb indexes was significantly higher in group 1 patients than in group 2 (P < 0.02) and group 3 patients (P < 0.01). Patients with at least 1 DQB1*02 allele showed more often a typical CD and diffuse histological lesions than did patients in the other groups.

CONCLUSIONS

The study demonstrates that tTGAb titers are HLA-DQB1*02 dose dependent, with significantly higher levels in homozygous individuals. Moreover, individuals with at least 1 HLA-DQB1*02 allele tend to have a more expressed clinical and histological form of celiac disease.

HLA DQ gene dosage and risk and severity of celiac disease

BACKGROUND & AIMS

Celiac disease (CD) is a chronic inflammatory disorder of the small intestine that is strongly associated with certain HLA molecules encoded by DQA and DQB genes. The aim of this study was to examine the role of DQA and DQB alleles in determining the risk for and the age of onset and severity of CD in an American population.

METHODS

High-resolution class 2 HLA genotyping was performed in a population-based sample (n = 84) of southeastern Minnesota residents with CD and a comparable control group (n = 102) to determine the contribution of DQA and DQB alleles to disease risk. Logistic regression modeling was used to examine the relative and absolute risks of CD.

RESULTS

Ninety-seven percent of CD patients carried both of the HLA alleles, DQA1*05 and DQB1*02. Those who carried a second allele of DQB1*02 were 5 times more likely to have CD than those with just one (95% confidence interval, 1.4-18.1). The carriage of 2 copies of DQB1*02 did not predict either an earlier age of onset or severity of disease.

CONCLUSIONS

Both HLA alleles DQA1*05 and DQB1*02 are associated with a greatly increased risk of CD, although the latter has the greater effect. Carrying 2 copies of DQB1*02 was associated with an even greater risk for disease but did not predict an earlier age of onset and diagnosis or disease severity. Assessing the copy number of the DQB1*02 allele might allow for the stratification of disease risk.

HLA-DQB1*0201 homozygosis predisposes to severe intestinal damage in celiac disease

OBJECTIVE

Celiac disease (CD) is a T-lymphocyte-mediated small intestinal enteropathy triggered and maintained by dietary gluten, with a strong genetic component mapping to the HLA genes encoding for the class II DQ(alpha1*0501, beta1*02) molecule. Damage of the small intestine may cause a variety of clinical signs ranging from isolated long-standing iron-deficiency anemia refractory to iron supplementation to forms of severe malnutrition that may become life threatening. However, patients carrying the typical intestinal lesions of CD and presenting no symptoms at all (silent CD) are also a common clinical observation. Since it is commonly assumed that clinical signs and symptoms tend to correlate with the severity of the intestinal damage, the purpose of this study was to investigate whether particular HLA class II genotypes might also influence the extent of intestinal damage and consequently the clinical presentation of the disease.

MATERIAL AND METHODS

We retrospectively compared histological grading of celiac disease intestinal biopsies with HLA haplotype, age at onset of disease and clinical signs and symptoms.

RESULTS

Our findings showed that homozygosis for the DQB1*0201 allele is associated with a higher severity of the histological score (p<0.008). Of note for the clinician, this work also suggests that the same type 3c of intestinal damage causes a different clinical syndrome, depending on the patient's age.

CONCLUSIONS

The genetic predisposition at the HLA-DQB1 locus influences the severity of the mucosal damage in a dose-dependent manner, but not the clinical presentation, of celiac disease.

Human leukocyte antigen-DQ2 homozygosity and the development of refractory celiac disease and enteropathy-associated T-cell lymphoma

BACKGROUND & AIMS

Celiac disease (CD) is a common gluten-sensitive enteropathy associated with human leukocyte antigen (HLA)-DQ2 and HLA-DQ8. The aim of this study was to determine if a particular HLA-DQ subtype predisposes to complications such as refractory CD with (RCD II) or without aberrant T cells (RCD I), and enteropathy-associated T-cell lymphomas (EATL).

METHODS

Molecular HLA-DQ typing was performed on 43 RCD I, 43 RCD II, and 30 EATL patients, and compared with age-matched groups of 121 patients with histologically defined uncomplicated CD and 183 healthy controls. All individuals were Dutch Caucasians and were at least 21 years of age.

RESULTS

HLA-DQ2 was present in 79% of RCD I, 97.7% of RCD II, and 96.6% of EATL patients. The differences were significant when compared with 28.9% in controls but not with 91.7% in uncomplicated CD. Homozygosity for HLA-DQ2 was observed in 25.5% of RCD I, 44.1% of RCD II, and 53.3% of EATL patients vs 20.7% of uncomplicated CD patients and 2.1% of controls. HLA-DQ8 was present in 10.7% of CD, 16.2% of RCD I, 9.3% of RCD II, and 6.6% of EATL patients vs 20.2% of controls.

CONCLUSIONS

Homozygosity for HLA-DQ2 is associated with RCD II and EATL. Early identification of HLA-DQ2 homozygous CD patients may help to recognize CD patients at risk for developing these severe complications.

Gene dose effect of the DQB1*0201 allele contributes to severity of coeliac disease

OBJECTIVE

Coeliac disease (CD) susceptibility has been shown to be associated with the HLA alleles DQA1*0501 and DQB1*0201. This HLA-associated risk has been estimated to account for 29-40% of the genetic component of CD. Conflicting data have been published on the gene dose effect of these HLA alleles on the risk and severity of CD. In this study the aim was to investigate the association between the number of HLA risk alleles and the severity of CD.

MATERIAL AND METHODS

Fifty-four Finnish CD families, including 144 CD patients mainly diagnosed in adulthood (94.4%), were enrolled in the study. The association between the number of DQA1*0501 and DQB1*0201 alleles and villous atrophy, symptoms and laboratory parameters at the time of diagnosis, and the association with villous atrophy after one year of treatment on a gluten-free diet were studied.

RESULTS

The homozygosity for the DQB1*0201 allele was associated with a more severe form of CD assessed by more severe villous atrophy (p=0.011), younger age (p=0.036), more severe diarrhoea (p=0.048) and a lower level of blood haemoglobin at the time of diagnosis (p=0.010). Furthermore, the homozygosity for the DQB1*0201 allele was associated with a slower recovery of villous atrophy after a gluten-free diet (p=0.041). In contrast, the DQA1*0501 allele did not have a significant association with the severity of CD.

CONCLUSIONS

Our results demonstrate a gene dose effect of the DQB1*0201 allele on the clinical heterogeneity of CD and on the rate of recovery from villous atrophy in patients on a gluten-free diet.

Should all children be screened for celiac disease?

To address the issue of screening children for celiac disease, current evidence has been summarized and placed within the context of 8 established criteria for childhood screening. Screening all children for celiac disease is not recommended at this time. Areas with gaps in knowledge are identified as areas in need of further study. These include the timing of screening, defining the natural history of screening-identified celiac disease, developing tools to predict disease onset and disease remission, and the risks of screening.

Allele and haplotype frequencies for HLA class II (DQA1 and DQB1) loci in patients with celiac disease from Spain

Celiac disease (CD) is a complex and multifactorial disease, defined as a malabsorptive disorder of the small intestine resulting from ingestion of gluten. Genetic susceptibility to CD has been associated with human leukocyte antigen (HLA)-DQ2 heterodimer, encoded by the DQA1*0501 and DQB1*02 genes. However, HLA risk factors do not explain the whole genetic predisposition: not all DQ2-encoding haplotypes confer equal susceptibility to CD. The aim of the present work was to confirm the aforementioned findings in a southern European population. With this purpose, 136 unrelated children diagnosed with CD were typed at the DNA level for HLA-DQA1 and -DQB1 loci. Patients are currently attended at the Donostia Hospital (province of Guipúzcoa, Spain). HLA class II typing was performed by polymerase chain reaction-sequence specific primer procedures. Conspicuous frequencies of the alleles associated with susceptibility to CD were observed (DQA1*0501: 0.592, DQB1*0201: 0.471). Accordingly, the haplotypes DQA1*0501-DQB1*0201 and DQA1*0201-DQB1*0202 revealed a strong linkage disequilibrium (18.84% and 18.75%, respectively) when compared with the Spanish general population. Of the total sample, 93.4% (127 individuals) were carriers of DQ2 heterodimer, either in homozygosis or in heterozygosis. This percentage coincides with figures reported in previous studies, implying the effect of other genes in the development of CD.

HLA types in celiac disease patients not carrying the DQA1*05-DQB1*02 (DQ2) heterodimer: results from the European Genetics Cluster on Celiac Disease

Genetic susceptibility to celiac disease is strongly associated with HLA-DQA1*05-DQB1*02 (DQ2) and HLA-DQA1*03-DQB1*0302 (DQ8). Study of the HLA associations in patients not carrying these heterodimers has been limited by the rarity of such patients. This European collaboration has provided a unique opportunity to study a large series of such patients. From 1008 European coeliacs, 61 were identified who neither carry the DQ2 nor DQ8 heterodimers. Fifty seven of these encoded half of the DQ2 heterodimer. The remaining 4 patients had a variety of clinical presentations. Three of them carried the DQA1*01-DQB*05 haplotype as did 20/61 of those carrying neither DQ2 nor DQ8. This may implicate a role of the DQA1*01-DQB*05 haplotype. None of these four patients carried the DQB1*06 allele that has previously been reported in this sub-group of patients. Of the 16 DQ2 heterodimer negative patients without DRB1*04 or DRB1*07 haplotypes, it was inferred that none encoded the previously implicated DRB4 gene as none had a DRB1*09 haplotype. These results underline the primary importance of HLA-DQ alleles in susceptibility to celiac disease, and the extreme rarity of celiac patients carrying neither the DQ2 or DQ8 heterodimers nor one half of the DQ2 heterodimer alone.

Genetic dissection between silent and clinically diagnosed symptomatic forms of coeliac disease in multiplex families

BACKGROUND

Coeliac disease has a large variation in clinical outcome. In addition to the classical disease with malabsorption, many individuals have a silent form, in which subject symptoms are missing but autoantibodies and mucosa lesions are identical to the symptomatic disease.

AIM

To investigate whether differences in HLA DR-DQ genes explain the variation in outcome.

MATERIALS AND METHODS

HLA DQ alleles were determined in 28 multiplex families with sibling pairs in which one had the symptomatic disease but the other had the silent form.

RESULTS

No differences in the distribution of HLA DR-DQ haplotypes could be observed. The clinically diagnosed coeliac disease seemed to have earlier onset than silent coeliac disease.

CONCLUSIONS

Results indicate that the major genetic susceptibility locus, HLA DQ, does not determine the exact clinical outcome of coeliac disease.

The genetics of autoimmune polyendocrine syndrome type II

A series of autoimmune disorders, often Addison's disease, type 1 diabetes mellitus, and thyroid autoimmunity, frequently occurs together in patients with the autoimmune polyendocrine syndrome type II (APS-II). The highest risk HLA genotype for Addison's disease, either as a single disease or in APS-II patients, consists of the genotype DR3/4, DQ2/DQ8 with DRB1*0404. As many as 30% of patients with Addison's disease have this genotype versus less than 0.5% of controls. An additional and important associated locus within the HLA region is the class I related gene, MIC-A. Patients who develop Addison's disease often have a delayed diagnosis and may die from Addisonian crisis; therefore, improved genetic testing combined with testing for 21-hydroxylase autoantibodies might allow the identification of relatively high-risk populations (greater than 1 in 200 defined genetic risk compared with 1 in 10,000 population risk).

HLA-DQA1 and HLA-DQB1 genetic markers and clinical presentation in celiac disease

BACKGROUND

Patients with celiac disease are diagnosed at any age and can exhibit a wide range of clinical manifestations. The reasons for this are unclear. The aim of this study was to investigate a possible correlation between the HLA-DQA1 and HLA-DQB1 genetic markers and clinical features of celiac disease.

METHODS

A total of 133 patients with celiac disease were tested for the HLA-DQA1 and HLA-DQB1 genes. Their corresponding allele and haplotype frequency distributions were estimated from the phenotypes found. The results were correlated with data from the clinical records.

RESULTS

The DQ2 molecule was found in 93% of the patients, and DQ2 or DQ8 was found in 98%. The DQA1*0201-DQB1*0202 haplotype showed strong linkage disequilibrium. DQ2 homozygosis was significantly associated with female sex, earlier age at diagnosis, and shorter delay between onset of symptoms and diagnosis. Double-dose DQB1*02 (01-02) allele was more frequent in patients with the classic presentation of the disease.

CONCLUSIONS

The genetic markers investigated may prove useful for diagnosing and managing celiac disease. With some clinical variables, correlations not previously described were found. These correlations have a moderate strength and, therefore, must be confirmed by other studies.

Coeliac disease and malignancy

The development of malignancy, particularly lymphoma, is the most serious complication to affect patients with coeliac disease. Although the association has been known for about 40 years, there are still gaps in our understanding. The prevalence of lymphoma and why only some coeliac patients develop this are not clear but environmental and genetic factors must be at work. Based on data from a large coeliac clinic in Derby, about 55 lymphomas per year would arise in the coeliac population of the United Kingdom, of which half would affect the small bowel. Whether patients with coeliac disease who have atypical or no symptoms at diagnosis, are at the same risk as those who are diagnosed as a result of classical symptoms as was more the case in the past, is not known. Some patients, however do have coeliac disease and lymphoma diagnosed at the same presentation. This consideration has implications for initiating screening programmes to detect coeliac disease and thus offer patients a gluten-free diet early that would help to reduce the risk of lymphoma from developing. In this context, case-finding rather than blanket population screening is to be recommended on present evidence. Research into the role of intraepithelial lymphocytes in the genesis of lymphoma has indicated that non-responsive coeliac disease (refractory sprue) and ulcerative jejunoileitis (ulcerative jejunitis) are part of the lymphoma spectrum. The diagnosis of lymphoma can be difficult and the prognosis, in general, is poor, although with modern chemotherapeutic regimes and surgery in selected cases, long-term survival is possible. The best option is to try and prevent lymphoma from arising by advising all patients to adhere to a strict gluten-free diet. Malignant complications of coeliac disease are uncommon but will continue to challenge clinicians and clinical scientists. Unravelling the mechanisms that contribute to the development of lymphoma and other tumours in coeliac disease may well contribute to a wider understanding of oncogenesis.

HLA-DQ typing in the diagnosis of celiac disease

OBJECTIVE

More than 95% of celiac patients share the major histocompatibility complex II class human leukocyte antigen (HLA) DQ2 or DQ8 haplotype; patients negative for both types are unlikely to suffer from celiac disease. Our aim was to investigate whether HLA-DQ2 and -DQ8 typing is helpful when diagnosis is uncertain because of the absence of unequivocal small bowel villous atrophy.

METHODS

HLA-DQ2 and -DQ8 typing was carried out in 59 patients evincing nondiagnostic small bowel mucosal lesion or positive celiac serology, and in 17 patients maintaining a gluten-free diet without biopsy-proven celiac disease. HLA findings were compared to small bowel mucosal morphology; intraepithelial lymphocytes; and serum endomysial (EmA), reticulin, tissue transglutaminase (anti-tTG) and gliadin antibodies.

RESULTS

Of the 59 patients evincing only minor small bowel mucosal changes or positive celiac disease serology, 22 (37%) were negative for DQ2 and DQ8. All EmA-positive patients had celiac-type HLA, but antireticulin antibody, anti-tTg, and antigliadin antibody were also present in HLA-DQ2- and -DQ8-negative individuals. Eleven of 17 patients (65%) observing a gluten-free diet before small bowel biopsy did not share celiac-type HLA. None of the 17 had apparent villous atrophy. Serum EmA and anti-tTG were negative in all. HLA-DQ typing is less expensive than follow-up biopsy in the exclusion of celiac disease.

CONCLUSIONS

HLA-DQ2 and -DQ8 determination is useful in exclusion, probably lifelong, of celiac disease in individuals with an equivocal small bowel histological finding. The low specificity of this test must, however, be borne in mind.