Autoimmune diseases co-occurring within individuals and within families: a systematic review

Genetics of type 1 diabetes and autoimmune thyroid disease

The search for the susceptibility alleles for the complex genetic conditions of type 1 diabetes and autoimmune thyroid diseases has gained momentum in recent years. Studies have revealed several novel disease susceptibility alleles of relevance to both conditions, which brings the total number of genetic variants contributing to type 1 diabetes to ten. Additional genetic loci remain to be discovered, particularly in the autoimmune thyroid diseases. In the future, the density and coverage of single nucleotide polymorphisms available for high throughput genotyping will improve, and detailed analysis of the role of copy number variants in these diseases will shed new light on the pathogenesis of these common endocrinopathies.

Major histocompatibility complex class II (DRB1*, DQA1*, and DQB1*) and DRB1*04 subtypes' associations of Hashimoto's thyroiditis in a Greek population

Hashimoto's thyroiditis (HT) is an autoimmune disease resulting from complex interactions between genetic and environmental factors. The disease is associated with certain human leukocyte antigen (HLA) class II alleles in various populations. We aimed to determine in this study, for the first time in a Greek population, the association of HLA-DRB1*, -DQA1*, and -DQB1* alleles with HT. HLA-DRB1*, -DQA1*, and -DQB1* alleles' and -DRB1*04 subtypes' distribution was evaluated in 125 patients with HT and in 500 healthy control individuals by using a DNA-based sequence-specific primer method. Chi(_)squared tests and Bonferroni correction method were applied in the statistical analysis of the data. Significantly higher frequency of DRB1*04 (24.8% vs 7.7%, P < 0.0001) was observed in HT patients, while HLA-DRB1*07 was significantly decreased (2.8% vs 7.9%, P < 0.05). HLA-DRB1*04 subtyping showed a significant increase of DRB1*0405 (21% vs 7.8%, P < 0.0001) in HT patients. Also significant high frequencies of DQB1*0201 (14.8% vs 8.2%, P < 0.001), DQB1*0302 (18.8% vs 7.0%, P < 0.0001), and DQA1*0301 (25.6% vs 7.8%, P < 0.0001) were recorded in the patient group. Conducting the first research of this kind in a Greek population, our study tries to provide an evaluation of the prevalence of HT relating to HLA-DRB1*0405, and we report a relative risk of 2.7 for HT in a Greek population.

Specific association of type 1 diabetes mellitus with anti-cyclic citrullinated peptide-positive rheumatoid arthritis

OBJECTIVE

The co-occurrence of autoimmune diseases such as rheumatoid arthritis (RA) and type 1 diabetes mellitus (DM) has been reported in individuals and families. In this study, the strength and nature of this association were investigated at the population level in a Swedish case-control cohort.

METHODS

For this case-control study, 1,419 patients with incident RA diagnosed between 1996 and 2003 were recruited from university, public, and private rheumatology units throughout Sweden; 1,674 matched control subjects were recruited from the Swedish national population registry. Sera from the subjects were tested for the presence of antibodies to cyclic citrullinated peptide (anti-CCP), rheumatoid factor (RF), and the 620W PTPN22 allele. Information on a history of diabetes was obtained by questionnaire, telephone interview, and/or medical record review. The prevalence of type 1 DM and type 2 DM was compared between patients with incident RA and control subjects and further stratified for the presence of anti-CCP, RF, and the PTPN22 risk allele.

RESULTS

Type 1 DM was associated with an increased risk of RA (odds ratio [OR] 4.9, 95% confidence interval [95% CI] 1.8-13.1), and this association was specific for anti-CCP-positive RA (OR 7.3, 95% CI 2.7-20.0), but not anti-CCP-negative RA. Further adjustment for the presence of PTPN22 attenuated the risk of anti-CCP-positive RA in patients with type 1 DM to an OR of 5.3 (95% CI 1.5-18.7). No association between RA and type 2 DM was observed.

CONCLUSION

The association between type 1 DM and RA is specific for a particular RA subset, anti-CCP-positive RA. The risk of developing RA later in life in patients with type 1 DM may be attributed, in part, to the presence of the 620W PTPN22 allele, suggesting that this risk factor may represent a common pathway for the pathogenesis of these 2 diseases.

Identification of AF4/FMR2 family, member 3 (AFF3) as a novel rheumatoid arthritis susceptibility locus and confirmation of two further pan-autoimmune susceptibility genes

The concept of susceptibility genes common to different autoimmune diseases is now firmly established with previous studies demonstrating overlap of loci conferring susceptibility to type 1 diabetes (T1D) with both Coeliac disease and multiple sclerosis. Rheumatoid arthritis (RA) is an archetypal autoimmune disease and we, therefore, targeted putative T1D susceptibility loci for genotyping in UK RA cases and unrelated controls. A novel RA susceptibility locus at AFF3 was identified with convincing evidence for association in a combined sample cohort of 6819 RA cases and 12 650 controls [OR 1.12 95% confidence intervals (CI) 1.07–1.17, P = 2.8 × 10⁻⁷]. Association of two previously described loci (CTLA-4 and 4q27) with RA was also replicated (OR 0.87, 95% CI 0.82–0.94, P = 1.1 × 10⁻⁴ and OR 0.86, 95% CI 0.79–0.94, P = 5.4 × 10⁻⁴, respectively). These findings take the number of established RA susceptibility loci to 13, only one of which has not been associated with other autoimmune diseases.

Are individuals with an autoimmune disease at higher risk of a second autoimmune disorder?

Limited evidence suggests that autoimmune diseases tend to co-occur, although data are needed to determine whether individuals with an existing autoimmune disorder are at increased risk of a second disorder. The authors conducted a series of population-based cohort studies, utilizing the United Kingdom General Practice Research Database, to assess intraindividual risks of coexistence of rheumatoid arthritis (RA), autoimmune thyroiditis (AIT), multiple sclerosis (MS), and insulin-dependent diabetes mellitus (IDDM) during 1990-1999. Sex-specific age- and calendar-period standardized incidence ratios (SIRs) were calculated for development of a second autoimmune disease among index populations including 22,888 RA, 26,198 AIT, 4,332 MS, and 6,170 IDDM patients compared with the general population. Among those with IDDM, adjusted AIT rates were higher than expected for both males (SIR = 646.0, 95% confidence interval (CI): 466, 873) and females (SIR = 409.6, 95% CI: 343, 485), as were RA rates for females (SIR = 181.6, 95% CI: 136, 238). Coexistence of AIT and RA was also shown for either disease sequence (sex-specific SIRs = 130.4-162.0). However, point estimates suggested an inverse relation between RA and MS, irrespective of diagnostic sequence. This study demonstrates coexistence of RA, AIT, and IDDM at higher than expected rates but reduced comorbidity between RA and MS.

Copy number variation in the human genome and its implication in autoimmunity

The causes of autoimmune disease remain poorly defined. However, it is known that genetic factors contribute to disease susceptibility. Hitherto, studies have focused upon single nucleotide polymorphisms as both tools for mapping and as probable causal variants. Recent studies, using genome-wide analytical techniques, have revealed that, in the genome, segments of DNA ranging in size from kilobases to megabases can vary in copy number. These changes of DNA copy number represent an important element of genomic polymorphism in humans and in other species and may therefore make a substantial contribution to phenotypic variation and population differentiation. Furthermore, copy number variation (CNV) in genomic regions harbouring dosage-sensitive genes may cause or predispose to a variety of human genetic diseases. Several recent studies have reported an association between CNV and autoimmunity in humans such as systemic lupus, psoriasis, Crohn's disease, rheumatoid arthritis and type 1 diabetes. The use of novel analytical techniques facilitates the study of complex human genomic structures such as CNV, and allows new susceptibility loci for autoimmunity to be found that are not readily mappable by single nucleotide polymorphism-based association analyses alone.

Detecting shared pathogenesis from the shared genetics of immune-related diseases

Recent genetic studies have revealed shared immunological mechanisms in several immune-related disorders that further our understanding of the development and concomitance of these diseases. Our Review focuses on these shared aspects, using the novel findings of recently performed genome-wide association studies and non-synonymous SNP scans as a starting point. We discuss how identifying new genes that are associated with more than one autoimmune or chronic inflammatory disorder could explain the genetic basis of the shared pathogenesis of immune-related diseases. This analysis helps to highlight the key molecular pathways that are involved in these disorders and the potential roles of novel genes in immune-related diseases.

Polyautoimmunity and familial autoimmunity in systemic sclerosis

Characterization of the extent to which particular combinations of autoimmune diseases occur in excess of that expected by chance may offer new insights into possible common pathophysiological mechanisms. The goal of this study was to investigate the spectrum of polyautoimmunity (i.e. autoimmune diseases co-occurring within patients) and familial autoimmunity (i.e. diverse autoimmune diseases co-occurring within families) in patients with systemic sclerosis (SSc). A cross-sectional study of two convenience samples of patients with SSc, one in Canada and the other in Colombia, was performed. History of other autoimmune diseases in the SSc patients as well as a family history of autoimmunity was obtained. Of 719 patients, 273 (38%) had at least one other autoimmune disease. A total of 366 autoimmune diseases were reported, of which the most frequent were autoimmune thyroid disease (AITD, 38%), rheumatoid arthritis (RA, 21%), Sjögren's syndrome (18%), and primary biliary cirrhosis (4%). There were 260 (36%) patients with first-degree relatives with at least one autoimmune disease, of which the most frequent were RA (18%) and AITD (9%). Having at least one first-degree relative with autoimmune disease was a significant predictor of polyautoimmunity in SSc patients. No significant differences in polyautoimmunity or familial autoimmunity were noted between diffuse and limited subsets of disease. Our results indicate that polyautoimmunity is frequent in patients with SSc and autoimmune diseases cluster within families of these patients. Clinically different autoimmune phenotypes might share common susceptibility variants, which acting in epistatic pleiotropy may represent risk factors for autoimmunity.

Autoimmune diseases in patients with multiple sclerosis and their first-degree relatives: a nationwide cohort study in Denmark

BACKGROUND

Multiple sclerosis (MS) and other autoimmune diseases might cluster. Our aim was to estimate the relative risk (RR) of other autoimmune diseases among MS patients and their first-degree relatives in a population-based cohort study.

METHODS

Using the Danish Multiple Sclerosis Register, the Danish Hospital Discharge Register, and the Danish Civil Registration System, we estimated RRs for 42 different autoimmune diseases in a population-based cohort of 12 403 MS patients and 20 798 of their first-degree relatives. Ratios of observed to expected numbers of autoimmune diseases, based on national sex-, age-, and period-specific incidence rates, served as measures of the RRs.

RESULTS

Compared with the general population, MS patients were at an increased risk of developing ulcerative colitis (RR = 2.0 (95% confidence interval (CI): 1.4-2.8), n = 29) and pemphigoid (RR = 15.4 (CI: 8.7-27.1), n = 12) but at reduced risk of rheumatoid arthritis (RR = 0.5 (CI: 0.4-0.8), n = 28) and temporal arteritis (RR = 0.5 (CI: 0.3-0.97), n = 11). First-degree relatives of MS patients were at increased risks of Crohn's disease (RR = 1.4 (CI: 1.04-1.9), n = 44), ulcerative colitis (RR = 1.3 (CI: 0.99-1.7), n = 51), Addison's disease (RR = 3.4 (CI: 1.3-9.0), n = 4), and polyarteritis nodosa (RR = 3.7 (CI: 1.4-10.0), n = 4).

CONCLUSION

PATIENTS

with MS and their first-degree relatives seem to be at an increased risk of acquiring certain other autoimmune diseases.

Allergy, family history of autoimmune diseases, and the risk of multiple sclerosis

OBJECTIVE

Previous reports suggested an association between allergy, autoimmunity, and risk of multiple sclerosis (MS), but results have been inconsistent. The present study assessed the association between history of allergy and autoimmune diseases, and the risk of MS.

METHODS

We conducted a case-control study nested in the Nurses' Health Study (NHS) and NHS II cohorts. A total of 298 women with MS were matched with 1248 healthy controls and 248 women with history of breast cancer. A mailed questionnaire gathered information about history of allergic conditions and autoimmune disorders.

RESULTS

History of allergy was not associated with MS risk [odds ratio (OR) 1.0, 95% confidence interval (CI) 0.8-1.4]. As expected, cases were more likely to have a positive family history of MS than controls (OR 9.7, 95% CI 6.1-15.3). A modest association was found between family history of other autoimmune diseases and MS risk (OR 1.4, 95% CI 1.0-1.8). We obtained similar results when we used women with breast cancer as comparison group.

CONCLUSION

Family history of other autoimmune diseases was associated with a higher MS risk, suggesting a common genetic background or shared environmental triggers. There was no clear association between personal history of allergy and risk of MS.

Epidemiology of autoimmune diseases in Denmark

An epidemiologic study of the autoimmune diseases taken together has not been done heretofore. The National Patient Register of Denmark is used to estimate the population prevalence of 31 possible or probable autoimmune diseases. Record linkage is used to estimate 465 pairwise co-morbidities in individuals among the 31 diseases, and familial aggregation among sibs, parents and offspring. The prevalence of any of the 31 diseases in the population is more than 5%. Within individuals, there is extensive comorbidity across the 31 diseases. Within families, aggregation is strongest for individual diseases and weak across diseases. These data confirm the importance of the autoimmune diseases as a group and suggest that common etiopathologies exist among them.

[Comorbidity in rheumatoid arthritis of early onset. Effects on outcome parameters]

Three-year follow-up data of 1,032 patients with recent onset rheumatoid arthritis (RA) were analyzed regarding the frequency of 21 common comorbid chronic conditions and their impact on health outcome (i.e., pain, functional capacity, disease activity, and radiographic joint damage). Multivariate logistic regression analyses were used to calculate age- and gender-adjusted odds ratios for each chronic condition on severe functional capacity (<60% of full function). Comorbidity was already common at the onset of RA, with 72% of the patients having at least one comorbid condition and almost 50% having at least two. Common comorbidities were associated with significantly worse baseline measures in at least three of seven investigated outcome parameters. The more of these conditions patients had, the worse their 3-year outcome. Functional capacity was most sensitive to comorbid conditions. In logistic regression, obesity, hypercholesterolemia, type II diabetes, and osteoporosis resulted in a twofold risk of severe functional limitation (<60% of full function), independent of each other and of age and gender. The impact of comorbidity on measures of disease severity should be considered when used to compare outcome parameters of different RA samples.

Prevalence of thyroid autoimmunity in sporadic idiopathic hypoparathyroidism in comparison to type 1 diabetes and premature ovarian failure

CONTEXT

Thyroid autoimmunity is the most common coexistent endocrinopathy in type 1 diabetes (T1D), Addison's disease, and premature ovarian failure (POF). Although the role of autoimmunity is being investigated in patients with sporadic idiopathic hypoparathyroidism (SIH), there is little information on coexistent thyroid autoimmunity.

OBJECTIVE

Our objective was to assess the prevalence of thyroid peroxidase autoantibodies (TPOAb) and thyroid dysfunction in patients with SIH and its comparison with that in T1D, POF, and Hashimoto's thyroiditis (HT) and age- and sex-matched healthy controls (for SIH).

DESIGN AND SETTING

We conducted a case control study in a tertiary care setting.

PATIENTS AND METHODS

Subjects were consecutive patients with SIH (n = 87), T1D (n = 100), POF (n = 58), and HT (n = 47) and healthy controls (100 females and 64 males). Serum free T3, free T4, TSH, and TPOAb (normal < or = 34 IU/ml) were measured by electrochemiluminescence assay. Subjects with 1) serum TSH at least 5 microU/ml along with TPOAb more than 34 IU/ml; 2) TSH at least 10 microU/ml but normal TPOAb titers; or 3) Graves' disease were considered to have thyroid dysfunction.

RESULTS

TPOAb positivity (> 34 IU/ml) in females was 14.6% in SIH, 24.1% in POF, and 42.1% in T1D compared with 76.6% in HT and 9% in healthy controls. The frequencies of TPOAb positivity and thyroid dysfunction in patients with SIH were comparable to those in control and POF groups, but significantly less than in T1D and HT groups.

CONCLUSION

The frequencies of TPOAb and thyroid dysfunction were not significantly higher in patients with SIH than in healthy controls, unlike in patients with T1D and POF.