Genome-wide analysis of extended pedigrees confirms IL2-IL21 linkage and shows additional regions of interest potentially influencing coeliac disease risk.

Coeliac disease is a chronic inflammatory condition of the small intestine, triggered by dietary exposure to gluten in genetically susceptible individuals. Risk alleles at HLA-DQA1 and HLA-DQB1 are necessary for disease development, but are alone not sufficient for disease onset. We aimed to identify novel loci underlying susceptibility to coeliac disease through the use of extended Finnish and Hungarian families with multiple affected individuals. An initial whole-genome linkage approach yielded several loci that were followed up further using the Immunochip custom array. Loci with a parametric logarithm of odds (LOD) score of >1.3 were identified at 4q, 6p [human leukocyte antigen (HLA) region], 6q, 7p, 17p, 17q and at 22p. The 4q and 6q loci have been identified previously in coeliac disease risk, whereas follow-up analyses indicate that the 17p and 22p loci may be novel risk loci for coeliac disease. These loci harbour previously described risk variants for other autoimmune diseases, but their segregation patterns do not explain the linkage to coeliac disease. We followed up the linkage to the 4q region, containing the previously described interleukin (IL)2 and IL21 genes. The risk variants at 4q in the studied pedigrees are most likely distinct from previously described risk variants, indicating that the observed linkage may be due to rare high-risk variants of still unknown nature. The importance of this locus to coeliac disease risk was further shown by the finding that serum levels of IL21 were elevated in both untreated and treated coeliac patients compared to controls.

Myosin IXB gene region and gluten intolerance: linkage to coeliac disease and a putative dermatitis herpetiformis association.

BACKGROUND: Coeliac disease is caused by dietary gluten, which triggers chronic inflammation of the small intestine in genetically predisposed individuals. In one quarter of the patients the disease manifests in the skin as dermatitis herpetiformis. Recently, a novel candidate gene, myosin IXB on chromosome 19p13, was shown to be associated with coeliac disease in the Dutch and Spanish populations. The same gene has previously been associated with inflammatory bowel disease, systemic lupus erythematosus and rheumatoid arthritis risk, making myosin IXB a potential shared risk factor in these inflammatory disorders. METHODS: In this study, previously reported myosin IXB variants were tested for genetic linkage and association with coeliac disease in 495 Hungarian and Finnish families and in an additional 270 patients and controls. RESULTS AND CONCLUSION: The results show significant linkage (logarithm of odds (LOD) 3.76, p = 0.00002) to 19p13 which supports the presence of a genuine risk factor for coeliac disease in this locus. Myosin IXB variants were not associated with coeliac disease in this study; however, weak evidence of association with dermatitis herpetiformis was found. The association could not explain the strong linkage seen in both phenotypes, indicating that the role of other neighbouring genes in the region cannot be excluded. Therefore, more detailed genetic and functional studies are required to characterise the role of the myosin IXB gene in both coeliac disease and dermatitis herpetiformis.

Increasing prevalence of coeliac disease over time.

BACKGROUND: The number of coeliac disease diagnoses has increased in the recent past and according to screening studies, the total prevalence of the disorder is around 1%. AIM: To establish whether the increased number of coeliac disease cases reflects a true rise in disease frequency. METHODS: The total prevalence of coeliac disease was determined in two population-based samples representing the Finnish adult population in 1978-80 and 2000-01 and comprising 8000 and 8028 individuals, respectively. Both clinically-diagnosed coeliac disease patients and previously unrecognized cases identified by serum endomysial antibodies were taken into account. RESULTS: Only two (clinical prevalence of 0.03%) patients had been diagnosed on clinical grounds in 1978-80, in contrast to 32 (0.52%) in 2000-01. The prevalence of earlier unrecognized cases increased statistically significantly from 1.03% to 1.47% during the same period. This yields a total prevalence of coeliac disease of 1.05% in 1978-80 and 1.99% in 2000-01. CONCLUSIONS: The total prevalence of coeliac disease seems to have doubled in Finland during the last two decades, and the increase cannot be attributed to the better detection rate. The environmental factors responsible for the increasing prevalence of the disorder are issues for further studies.

Unusual manifestations of celiac disease.

Celiac disease is multifaced autoimmune disorder with several extraintestinal manifestations and connections to other autoimmune diseases and other conditions. The recognition of the complex clinical picture of the disease helps doctors to search and diagnose celiac disease even if the gastrointestinal symptoms are lacking. Individuals at risk for celiac disease should be thoroughly investigated and individuals with unusual manifestations of the disease should be screened actively.

Oats in the treatment of childhood coeliac disease: a 2-year controlled trial and a long-term clinical follow-up study.

BACKGROUND: The exclusion of oats from the diet in coeliac disease is controversial. AIM: To study the long-term safety of oats in the treatment of children with coeliac disease. METHODS: Altogether 32 children with coeliac disease were enrolled in a 2-year controlled trial. Twenty-three children in remission were randomized either to oats or gluten challenge; when small bowel histological relapse was evident after gluten challenge, a gluten-free diet including oats was started. Furthermore, nine newly detected coeliac patients adopted an oat-containing gluten-free diet. Small bowel mucosal morphology, CD3+, alphabeta+ and gammadelta+ intraepithelial lymphocytes, human leucocyte antigen (HLA) DR expression and coeliac serology were determined. After the trial, the children were allowed to eat oats freely; follow-up was extended up to 7 years. RESULTS: In coeliac children in remission, oats had no detrimental effect on intestinal histology or serology during the 2-year trial. In contrast, the gluten-challenge group relapsed after 3-12 months. Complete recovery from the disease was accomplished in all relapsed and newly detected patients on an oat-containing gluten-free diet. After the trial, 86% of the children preferred to consume oats and they all remained in remission. CONCLUSION: In most children with coeliac disease, long-term consumption of oats is well tolerated, and it does not result in small bowel mucosal deterioration or immune activation.

Cytokine gene polymorphisms and genetic association with coeliac disease in the Finnish population.

Coeliac disease (CD) is an intestinal disorder caused by intolerance to dietary gluten in susceptible individuals. The HLA-DQ genes are major risk factors for CD, but other genes also play an important role in the disease susceptibility. Immune-mediated mechanisms are known to underlie the pathogenesis of CD. We studied single-nucleotide polymorphisms in transforming growth factor (TGF)-beta1, interleukin (IL)-10, IL-6, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha genes in the Finnish population using family-based association approach. In addition, we genotyped a trinucleotide repeat polymorphism in the major histocompatibility complex (MHC) class I chain-related protein A (MICA) gene, located in the human leucocyte antigen (HLA) region in the vicinity of TNF-alpha. To control the effect of linkage disequilibrium between HLA-DQ genes and MICA and TNF-alpha, an HLA-stratified association analysis was performed. We did not find evidence of association between TGF-beta1, IL-10, IL-6 and IFN-gamma polymorphisms and CD susceptibility. No association was found for any of the MICA alleles independently of DQ genes, whereas TNF-alpha-308 A allele was slightly overrepresented on chromosomes carried by CD patients compared with control chromosomes, indicating that either TNF-alpha, or another gene in linkage disequilibrium with it, could confer increased susceptibility to CD. This result supports the earlier findings that the HLA region harbours a novel susceptibility factor in addition to HLA-DQ.

Effect of an oats-containing gluten-free diet on symptoms and quality of life in coeliac disease. A randomized study.

BACKGROUND: Evidence suggests the acceptability of oats in a gluten-free diet in coeliac disease. We investigated the impact of an oats-containing diet on quality of life and gastrointestinal symptoms. METHODS: Thirty-nine coeliac disease patients on a gluten-free diet were randomized to take either 50 g of oats-containing gluten-free products daily or to continue without oats for 1 year. Quality of life was assessed using the Psychological General Well-Being questionnaire and gastrointestinal symptoms using the Gastrointestinal Symptom Rating Scale. Small-bowel mucosal villous architecture, CD3+, alphabeta+, gammadelta+ intraepithelial lymphocytes, serum endomysial and tissue transglutaminase antibodies were investigated. RESULTS: Twenty-three subjects were randomized to the oats-containing diet and 16 to the traditional gluten-free diet. All adhered strictly to their respective diet. Quality of life did not differ between the groups. In general, there were more gastrointestinal symptoms in the oats-consuming group. Patients taking oats suffered significantly more often from diarrhoea, but there was a simultaneous trend towards a more severe average constipation symptom score. The villous structure did not differ between the groups, but the density of intraepithelial lymphocytes was slightly but significantly higher in the oats group. The severity of symptoms was not dependent on the degree of inflammation. Antibody levels did not increase during the study period. CONCLUSION: The oats-containing gluten-free diet caused more intestinal symptoms than the traditional diet. Mucosal integrity was not disturbed, but more inflammation was evident in the oats group. Oats provide an alternative in the gluten-free diet, but coeliac patients should be aware of the possible increase in intestinal symptoms.

Genetic association of coeliac disease susceptibility to polymorphisms in the ICOS gene on chromosome 2q33.

An interesting candidate gene region for coeliac disease (CD), a common multifactorial disease, is a segment on 2q33-37 harbouring the genes for the CD28, cytotoxic T-lymphocyte-associated antigen-4 (CTLA4), inducible costimulator (ICOS), and programmed death-1 (PD-1), all receptors that regulate lymphocyte activation. Several studies have suggested a role for this locus in immune-mediated diseases. To study further our previous finding of genetic linkage of this region to CD, we studied 25 polymorphic markers to identify the putative disease-associated polymorphism. Transmission/disequilibrium test in 106 Finnish families with CD indicated that only four polymorphisms, all located in the ICOS gene, showed evidence for genetic association. Strong linkage disequilibrium (LD), based on the analysis of 424 haplotypes, encompassed not only the associated ICOS markers but also many polymorphisms in the CTLA4 gene. Our results demonstrate that due to LD, it appears not easy to identify the genuine susceptibility factor in this region without larger multipopulation studies. Furthermore, the results did not support the evidence that polymorphisms in CTLA4 were the major susceptibility locus for CD.

Additional factor in some HLA DR3/DQ2 haplotypes confers a fourfold increased genetic risk of celiac disease.

Although HLA-DQ genes are the major celiac disease (CD) susceptibility genes, results from Finnish families suggest that not all DQ2-encoding haplotypes confer equal susceptibility to CD, implying the effect of other gene(s) in the HLA region. The aim of the present work was to extend and confirm the aforementioned results in a southern European population ( Italian) and to better localize the additional risk factor/s. The association of nine loci spanning the HLA region from DR to HFE, 4.5-Mb telomeric of HLA-A, was tested. The analysis was performed by comparing marker frequencies in DR3-DQ2 haplotypes transmitted and non-transmitted to the affected offspring in 156 Italian CD families selected for having at least one DR3-positive parent. The same analysis was performed independently in 101 Finnish CD families selected with the same criteria. Three alleles, MICA-A5.1, MICB-CA24 and MIB-350, all characteristic of the B8-DR3 extended haplotype, showed a significantly increased frequency in DR3 transmitted haplotypes in the Italian families. DR3 haplotypes carrying the combination of these alleles conferred an approximate fourfold increased CD risk. B8-DR3 transmitted haplotypes were significantly more conserved telomerically down to the MIC-Class I region. Similar results were seen in the Finnish families. The major conclusion that holds true in both populations is that, while DQ2 is an absolute requirement for the development of CD, the presence of an additional genetic factor within the MIC-Class I region confers an approximate 4-fold increased risk of the disease.

Genetic dissection between coeliac disease and dermatitis herpetiformis in sib pairs.

Gluten sensitive enteropathy has various manifestations, of which the two major forms are classical coeliac disease (cCD) and dermatitis herpetiformis (DH). In cCD predominantly the small intestine is affected, whereas in DH also the skin is affected showing typical rash and IgA deposits. The symptoms in both forms are dependent on gluten intake. The factors diversifying these two clinical outcomes are unknown. In the present report we evaluated the role of the major genetic susceptibility locus, HLA DQ, in 25 families, in which both forms of the disease, cCD and DH, occurred in siblings. By using the family-based approach it can be assumed that within each family variation in environmental factors is substantially lower than in the standard case-control setting, and also the problems related to population stratification can be avoided. Results from the Finnish family material with 25 discordant and 85 concordant sib pairs, and from additional case-control material comprising 71 unrelated Hungarian DH and 68 cCD patients, together indicated that the HLA DQ locus did not differ between the two major outcomes of gluten sensitive enteropathy. The non-HLA DR;DQ factors are critical for the different clinical manifestations of gluten sensitivity.

CD80 (B7-1) and CD86 (B7-2) genes and genetic susceptibility to coeliac disease.

The role of the costimulatory molecules B7-1 (CD80) and B7-2 (CD86) in T-cell activation makes them good candidates for coeliac disease susceptibility genes. We conducted a genetic linkage study of the CD80/86 gene region in the general Finnish population and in a local subisolate. No linkage was found in either population.

Not all HLA DR3 DQ2 haplotypes confer equal susceptibility to coeliac disease: transmission analysis in families.

BACKGROUND: HLA-DQ is the only established susceptibility factor for coeliac disease. We tested whether all HLA haplotypes with the known risk marker, HLA-DQ2, confer equal susceptibility to coeliac disease, i.e. whether haplotype transmission from DQ2 homozygous parents to patients is random. The random transmission would strengthen the importance of DQ2 as the only risk factor within the HLA region. METHODS: Inheritance of DQ2-positive haplotypes from parent to patients was investigated in 14 of 127 Finnish coeliac families who had an HLA-DQ2 homozygous parent. HLA alleles and 18 HLA-linked microsatellite markers were used to determine the haplotypes, which were divided into those transmitted and those non-transmitted from DQ2-homozygous parents to patients: RESULTS: Transmitted haplotypes differed clearly from those not transmitted. The alleles in the transmitted haplotypes were strongly conserved and predominantly consisted of the well-known HLA-A*01, B*08, DRB1*03, DQ2, DPB1*0101 haplotype. The non-transmitted haplotypes, on the other hand, were significantly more heterogeneous; in particular, markers near HLA-A and -B genes differed from the transmitted haplotypes. CONCLUSIONS: The results suggest that DQ2 is not the only HLA-linked genetic risk factor for coeliac disease but the conserved haplotype harbours at least one other risk gene.

Coeliac disease among healthy members of multiple case coeliac disease families.

BACKGROUND: The main objective of the study was to assess the frequency of undetected coeliac disease among the first-degree relatives of families with two or more previously diagnosed coeliac disease patients. The value of the serum endomysial antibody test as a single means of detecting clinically silent coeliac disease was evaluated. The correlation of endomysial and tissue transglutaminase antibodies and the correlation of endomysial antibodies to the HLA typical for coeliac disease was determined. METHODS: A total of 137 multiple-case coeliac disease families with 872 family members were recruited; 466 healthy family members were simultaneously screened for gliadin and endomysial antibodies and thereafter for tissue tranglutaminase antibodies. Antibody-positive persons were typed for HLA-DQ2 and DQ8. The diagnosis of coeliac disease was based on the typical mucosal lesion on small-bowel biopsies. RESULTS: Forty-four (9.4%) of the healthy family members were positive for endomysial and 48 (10.3%) for gliadin antibodies; 42 biopsies revealed 29 new coeliac disease patients (6.2% of healthy individuals). Endomysial antibodies detected 97% and gliadin antibodies 52% of the new cases. All 44 endomysial-antibody-positive and 35 of 48 gliadin-antibody-positive individuals were positive for DQ2. Tissue transglutaminase antibodies corresponded well with endomysial antibodies. CONCLUSIONS: Undetected coeliac disease is common even among healthy first-degree relatives of multiple case families. The findings emphasize the value of serum endomysial antibodies in the detection of clinically silent coeliac disease. Endomysial-antibody-positive individuals, unlike gliadin-antibody-positive ones, share the coeliac disease-type HLA-DQ.

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.

Candidate gene region 15q26 and genetic susceptibility to coeliac disease in Finnish families.

BACKGROUND: Studies in the Irish and British populations have indicated that chromosome region 15q26 could include a novel non-HLA-linked locus conferring genetic susceptibility to coeliac disease. The locus is of particular interest, since a type I diabetes risk locus, IDDM3, maps to the same position. It was tested whether this locus shows evidence for genetic linkage to coeliac disease in Finland. METHODS: Ninety-nine Finnish families with at least one affected sibpair were studied. Five microsatellite markers mapped within approximately 20 cM region on chromosome 15q26 were typed. Non-parametric linkage (NPL) scores and allelic transmission (TDT) were studied. RESULTS: No evidence for genetic linkage could be obtained by the NPL scores calculated by the Genehunter program. However, transmission/disequilibrium analysis (TDT) revealed that haplotype D15S107*1-D15S120*6 was statistically significantly more frequently transmitted to affected than expected by chance (TDT chi2 9.0; P = 0.003). The subgroup of families having this haplotype, however, did not differ from the others, regarding to disease manifestation, HLA status, or geographical origin. CONCLUSION: The 15q26 region appears not to be a major non-HLA susceptibility locus for gluten sensitivity in Finland, but a particular haplotype which may harbour a susceptibility gene was identified.

Candidate gene regions and genetic heterogeneity in gluten sensitivity.

BACKGROUND: Gluten sensitivity is a common multifactorial disorder, manifested in the small intestine or on the skin as typical coeliac disease or dermatitis herpetiformis, respectively. The only established genetic risk factor is HLA DQ2. AIMS: We tested genetic linkage of previously reported chromosomal loci 5q and 11q in Finnish families with gluten sensitivity. We also tested if genetic linkage to candidate loci on 5q, 11q, 2q33, and HLA DQ differed with respect to clinical manifestations or sex. SUBJECTS: We studied 102 Finnish families with affected sibpairs. For heterogeneity analysis, families were divided into subgroups according to sex and the presence of dermatitis herpetiformis, the skin manifestation of gluten sensitivity. METHODS: Non-parametric linkage between microsatellite markers and disease was tested. Linkage heterogeneity between subgroups was tested using the M test. The transmission/disequilibrium test and association analysis were performed. RESULTS: Evidence of linkage to 11q (MLS 1.37), but not to 5q, was found in the entire dataset of 102 families. Heterogeneity between subgroups was suggested: families with only the intestinal disease showed linkage mainly to 2q33 whereas families with dermatitis herpetiformis showed linkage to 11q and 5q, but not to 2q33. Linkage in all three non-HLA loci was strongest in families with predominantly male patients. HLA DQ2 conferred much stronger susceptibility to females than males. CONCLUSIONS: Independent evidence for the suggested genetic linkage between 11q and gluten sensitivity was obtained. The possible linkage heterogeneity suggests genetic differences between intestinal and skin manifestations, and the gender dependent effect of HLA DQ2.

Use of closely related affected individuals for the genetic study of complex diseases in founder populations.

We propose a method, the maximum identity length contrast (MILC) statistic, to locate genetic risk factors for complex diseases in founder populations. The MILC approach compares the identity length of parental haplotypes that are transmitted to affected offspring with the identity length of those that are not transmitted to affected offspring. Initially, the statistical properties of the method were assessed using randomly selected affected individuals with unknown relationship. Because both nuclear families with multiple affected sibs and large pedigrees are often available in founder populations, we performed simulations to investigate the properties of the MILC statistic in the presence of closely related affected individuals. The simulation showed that the use of closely related affected individuals greatly enhances the power of the statistic. For a given sample size and type I error, the use of affected sib pairs, instead of affected individuals randomly selected from the population, could increase the power by a factor of two. This increase was related to an increase of kinship-coefficient contrast between haplotype groups when closely related individuals were considered. The MILC approach allows the simultaneous use of affected individuals from a founder population and affected individuals with any kind of relationship, close or remote. We used the MILC approach to analyze the role of HLA in celiac disease and showed that the effect of HLA may be detected with the MILC approach by typing only 11 affected individuals, who were part of a single large Finnish pedigree.

Osteopenia in patients with clinically silent coeliac disease warrants screening.

Bone-mineral density was measured in 19 clinically silent coeliac patients. The density was low, comparable with that in coeliac cases, and improved by gluten-free diet.

CD28/CTLA4 gene region on chromosome 2q33 confers genetic susceptibility to celiac disease. A linkage and family-based association study.

Celiac disease (CD) is a common small intestinal injury caused by sensitivity to gliadin in genetically-predisposed individuals. The only susceptibility locus established is the HLA-DQ. We tested whether the chromosomal region of the CD28/CTLA4 genes on 2q33 is linked to CD. These genes encode receptors regulating the T-lymphocyte activation. Recently, this gene region was reported to be linked to the susceptibility to many autoimmune diseases, including insulin-dependent diabetes (IDDM12locus). It is thus an obvious candidate locus also for CD, since the intestinal injury is mediated by the immune system. Genetic linkage between seven marker loci in this gene region and CD was studied in 69 Finnish families. In the multipoint linkage analysis, the highest non-pararametric linkage score (NPL) was 1.75 (P=0.04) for D2S116, suggesting weak linkage for this candidate locus. To evaluate this finding, an additional 31 families were typed for all markers. In the combined set of 100 families the NPL score for marker D2S116 was 2.55 (P=0.006) and for other markers 1.90-2.47 (P=0.029-0.007), supporting genuine linkage at this region. Significantly, locus D2S116 also showed a clear allelic association in these 100 families (P=0.0001). The transmission/disequilibrium test (TDT) for locus D2S116 gave preliminary evidence for preferential maternal non-transmission of allele *136 to patients (TDTmax=8.3; P<0.05). No paternal deviation was found suggesting that the effect of the locus might be mediated by a sex-dependent factor protective against CD. Our results indicate that the CD28/CTLA4 gene region can contain a novel susceptibility locus for CD and support the hypothesis that CD has an immune system-mediated component. Like the HLA, the CD28/CTLA4 genes appear to be associated with genetic susceptibility to various autoimmune diseases.