Familial risk estimation in systemic sclerosis

Immunogenetics of Systemic Sclerosis

Systemic sclerosis (SSc) is a rare autoimmune connective tissue disorder characterized by massive fibrosis, vascular damage, and immune imbalance. Advances in rheumatology and immunology over the past two decades have led to a redefinition of systemic sclerosis, shifting from its initial perception as primarily a "hyperfibrotic" state towards a recognition of systemic sclerosis as an immune-mediated disease. Consequently, the search for genetic markers has transitioned from focusing on fibrotic mechanisms to exploring immune regulatory pathways. Immunogenetics, an emerging field at the intersection of immunology, molecular biology, and genetics has provided valuable insights into inherited factors that influence immunity. Data from genetic studies conducted thus far indicate that alterations in genetic messages can significantly impact disease risk and progression. While certain genetic variations may confer protective effects, others may exacerbate disease susceptibility. This paper presents a comprehensive review of the most relevant genetic changes that influence both the risk and course of systemic sclerosis. Special emphasis is placed on factors regulating the immune response, recognizing their pivotal role in the pathogenesis of the disease.

Genetics of systemic sclerosis

Systemic sclerosis is an autoimmune disease characterized by generalized fibrosis in connective tissues and internal organs as consequences of microvascular dysfunction and immune dysfunctions, which leads to premature death in affected individuals. The etiology of systemic sclerosis is complex and poorly understood, but as with most autoimmune diseases, it is widely accepted that both environmental and genetic factors contribute to disease risk. During the last decade, the number of genetic markers convincingly associated with systemic sclerosis has exponentially increased. In this article, we briefly mention the genetic components of systemic sclerosis. Then, we review the classical and novel genetic associations with systemic sclerosis, analyzing the firmest and replicated signals within non-human leukocyte antigen genes, identified by both candidate gene approach and genome-wide association studies. We also provide an insight into the future perspectives that will shed more light into the complex genetic background of the disease. Despite the remarkable advance of systemic sclerosis genetics during the last decade, the use of the new genetic technologies such as next-generation sequencing, as well as the deep phenotyping of the study cohorts, to fully characterize the genetic component of this disease is imperative to identify causal variants, which leads to more targeted and effective treatment of systemic sclerosis.

Systemic sclerosis in mother and daughter with susceptible HLA haplotype and anti-topoisomerase I autoantibodies

Systemic sclerosis is a rare systemic autoimmune rheumatic disease which is thought to be polygenic disorder contributed by both genetic and environmental factors. A positive family history of SSc is the strongest risk factor yet identified for SSc; however, the absolute risk for each family member remains quite low. A systematic literature search was performed in MEDLINE and Scopus database for studies published only in English that investigated the prevalence of SSc in first-degree relatives of SSc patients and whether SSc family members have greater frequency of I autoantibodies (ATA) than expected. Following keywords and terms: "systemic sclerosis", "scleroderma", "familial","ATA", "topoisomerase", and "anti-Scl70" were used to select the appropriate articles. From the 21 initially identified articles, 16 were eliminated because of the inclusion criteria, and five articles concerning familial occurrence of SSc in first-degree relatives positive for ATA were included for further analysis. Two case reports were described-a daughter and a mother diagnosed with systemic sclerosis with ATA tested for specific genotype. In both cases, patients had antinuclear autoantibodies (ANA) at a titer of > 1:1280, AC-29 cell pattern according to ICAP, and their sera were positive for ATA. In addition, anti-SSA/Ro60 autoantibodies were found in the case of the mother. Complementary to ATA positivity, the daughter was also positive for AMA-M2 autoantibodies. The results showed that our patients shared HLA-DRB1*1104-DQA1*0501-DQB1*0301 haplotype and had positive ATA, which corresponds to the strong association between ATA in white subjects and HLA-DRB1*1104, DQA1*0501, DQB1*0301 haplotype (OR = 6.93). Our patients not only shared a risky HLA haplotype for SSc but also manifested with a similar immunological activity, given that they were both positive for ATA. Although infrequent, ATA-positive SSc patients could develop scleroderma renal crisis, as in the case of the mother. Therefore, careful monitoring of the renal function is the best strategy for the case of the daughter. A positive family history is an important hint for patients suspected of autoimmune disease. The cases of familial SSc are quite rare, but they give us the opportunity to compare the genetic background, environmental risk factors, SSc phenotype, ANA type, and prevention of the complications in the course of the disease.

New insights into the genetics and epigenetics of systemic sclerosis

Systemic sclerosis (SSc) is a severe autoimmune disease that is characterized by vascular abnormalities, immunological alterations and fibrosis of the skin and internal organs. The results of genetic studies in patients with SSc have revealed statistically significant genetic associations with disease manifestations and progression. Nevertheless, genetic susceptibility to SSc is moderate, and the functional consequences of genetic associations remain only partially characterized. A current hypothesis is that, in genetically susceptible individuals, epigenetic modifications constitute the driving force for disease initiation. As epigenetic alterations can occur years before fibrosis appears, these changes could represent a potential link between inflammation and tissue fibrosis. Epigenetics is a fast-growing discipline, and a considerable number of important epigenetic studies in SSc have been published in the past few years that span histone post-translational modifications, DNA methylation, microRNAs and long non-coding RNAs. This Review describes the latest insights into genetic and epigenetic contributions to the pathogenesis of SSc and aims to provide an improved understanding of the molecular pathways that link inflammation and fibrosis. This knowledge will be of paramount importance for the development of medicines that are effective in treating or even reversing tissue fibrosis.

A systematic review of the epidemiology, disease characteristics and management of systemic sclerosis in Australian adults

OBJECTIVE

Australia has one of the highest prevalence rates of systemic sclerosis (SSc) worldwide. In order to highlight management deficiencies and key areas for further research, it is essential to understand its local epidemiological patterns, natural history, prognosis and mortality trends over time.

METHODS

To identify Australian SSc-specific information through a systematic review focusing on areas of epidemiology, disease characteristics, treatment, functional ability, disease burden and health-related quality of life (HRQoL).

RESULTS

MEDLINE, EMBASE and the Cochrane Library were searched on 14 September, 2016. All original full text articles on SSc in Australia were included. Of the 54 articles included in this review, the majority of studies recruited from South Australia, Victoria and New South Wales. The prevalence of SSc in Australia is increasing and is similar among the general population and the Aboriginal population. Despite improvements in care over the last three decades, morbidity and mortality remain high, with an overall standardized mortality ratio of 3.4 and a 10-year survival of 84% in a newly diagnosed patient. Cardiorespiratory manifestations are the leading cause of SSc-related death. Malignancy is the leading cause of non-SSc-related death. The role of autoantibodies in predicting disease subtype, visceral involvement and their use as a prognostic marker is becoming increasingly recognized.

CONCLUSION

Information on SSc in Australia, particularly unmet healthcare needs, HRQoL and economic burden, is limited. As a heterogenous condition, SSc requires a multi-disciplinary approach to care. Research aimed at quantifying HRQoL and burden of disease in Australia is essential for advocacy and resource allocation.

Familial risk of systemic sclerosis and co-aggregation of autoimmune diseases in affected families

Background

Systemic sclerosis (SSc) is a rare and devastating disease affecting skin and internal organs. Familial aggregation of SSc and co-aggregation with other autoimmune diseases is rarely reported.

Methods

We identified 23,658,577 beneficiaries registered with the National Health Insurance database in 2010, 1891 of whom had SSc. We identified 21,009,551 parent–child relationships and 17,168,340 full sibling pairs. The familial risks of SSc and other autoimmune diseases and familial transmission were estimated.

Results

The prevalence of SSc in the general population was 0.008 %. There are 3801 individuals had at least one first-degree relative with SSc, among them 3 people had SSc which was equivalent to a prevalence of 0.08 %. The adjusted relative risk (RR) (95 % CI) for SSc was 81.21 (11.40–579.72) for siblings of SSc patients. The familial transmission (genetic plus shared environmental contribution to total phenotypic variance of SSc) was 0.72. However, 84.1 % of patients were expected to be sporadic cases. The RR (95 % CI) in first-degree relatives of SSc patients was 2.64 (1.46–4.75) for rheumatoid arthritis, 6.51 (4.05–10.46) for systemic lupus erythematosus, 2.77 (1.04–7.35) for Sjögren’s syndrome, 8.05 (2.03–31.92) for idiopathic inflammatory myositis, and 1.52 (1.15–2.01) for psoriasis.

Conclusions

The risks of SSc and other autoimmune diseases are increased in relatives of people with SSc, and family factors explain over two-thirds of the phenotypic variance of the disease. These findings may be useful in counselling families of patients with SSc and for further genetic studies.

Genetics of systemic sclerosis: recent advances

Purpose of review

Large-scale and follow-up genetic association studies in systemic sclerosis (SSc) have implicated over 40 regions in disease risk, 15 of which with robust associations. Nevertheless, the causal variants and the functional mechanisms underlying the genetic associations remain elusive, and the reasons for the higher disease burden in African Americans unknown. Incorporating tools from diverse fields is beginning to unveil the role of genetic diversity and regulatory variation in SSc susceptibility. This review will summarize recent advances in SSc genetics, including autoimmune disease overlap, evidence of natural selection, and current progress towards the dissection of the functional role of associated risk variants.

Recent findings

In the past year, multiple large-scale studies reported novel strong and suggestive SSc associations. These results, coupled with the regions shared with other autoimmune diseases, emphasize the role of dysregulation of immune pathways as a key causative factor in SSc pathogenesis. Strong evidence implicates natural selection as a mechanism contributing to the maintenance of some of these SSc alleles in the population. Studies integrating genomic, transcriptomic, and epigenomic datasets in specific cell types to identify causal autoimmune disease variants are emerging.

Summary

The identification and comprehensive understanding of the factors and mechanisms contributing to SSc will contribute to improved diagnosis and disease management.

The IL-33 gene is related to increased susceptibility to systemic sclerosis

Systemic sclerosis (SSc) is a chronic inflammatory disease characterized by widespread fibrosis of the skin and several visceral organs. The pro-fibrotic potential of interleukin (IL)-33 has been demonstrated by in both in vitro and in vivo settings; moreover, increased level of IL-33 has also been reported in patients with SSc. Therefore, the aim of the present study was to detect the potential association of IL-33 gene polymorphisms on the susceptibility of SSc. A total of 300 SSc patients and 280 healthy controls (HC) were enrolled in this multicentric preliminary candidate gene study. DNA samples were harvested using an appropriate commercial DNA isolation kit. Four single nucleotide polymorphisms (SNPs) of IL-33 gene (rs7044343, rs1157505, rs11792633 and rs1929992) were genotyped using the appropriate commercial primer/probe sets on real-time PCR. There was no significant difference in terms of the allelic distributions and minor allele frequencies of evaluated four IL-33 polymorphisms between the SSc and HC groups (P > 0.05 for all). Moreover, the genotypic distributions of rs1157505, rs11792633 and rs1929992 polymorphisms were not significantly different (P > 0.05 for all). However, CC genotype of rs7044343 SNP was significantly higher in the SSc group compared to the HC group (P = 0.013, OR 1.75, 95 % CI 1.12-2.72). This preliminary candidate gene study demonstrates that rs7044343 polymorphism of IL-33 gene is associated with the susceptibility to the SSc in Turkish population. It may be suggested that IL-33 gene may be a candidate gene to research in SSc.

Recent advances in the genetics of systemic sclerosis: toward biological and clinical significance

Significant advances have been made in understanding the genetic basis of systemic sclerosis (SSc) in recent years. Genomewide association and other large-scale genetic studies have identified 30 largely immunity-related genes which are significantly associated with SSc. We review these studies, along with genomewide expression studies, proteomic studies, genetic mouse models, and insights from rare sclerodermatous diseases. Collectively, these studies have begun to identify pathways that are relevant to SSc pathogenesis. The findings presented in this review illustrate how both genetic and genomic aberrations play important roles in the development of SSc. However, despite these recent discoveries, there remain major gaps between current knowledge of SSc, a unified understanding of pathogenesis, and effective treatment. To this aim, we address the important issue of SSc heterogeneity and discuss how future research needs to address this in order to develop a clearer understanding of this devastating and complex disease.

An Immunochip-based interrogation of scleroderma susceptibility variants identifies a novel association at DNASE1L3

Introduction

The aim of the study was to interrogate the genetic architecture and autoimmune pleiotropy of scleroderma susceptibility in the Australian population.

Methods

We genotyped individuals from a well-characterized cohort of Australian scleroderma patients with the Immunochip, a custom array enriched for single nucleotide polymorphisms (SNPs) at immune loci. Controls were taken from the 1958 British Birth Cohort. After data cleaning and adjusting for population stratification the final dataset consisted of 486 cases, 4,458 controls and 146,525 SNPs. Association analyses were conducted using logistic regression in PLINK. A replication study was performed using 833 cases and 1,938 controls.

Results

A total of eight loci with suggestive association (P <10^-4.5) were identified, of which five showed significant association in the replication cohort (HLA-DRB1, DNASE1L3, STAT4, TNP03-IRF5 and VCAM1). The most notable findings were at the DNASE1L3 locus, previously associated with systemic lupus erythematosus, and VCAM1, a locus not previously associated with human disease. This study identified a likely functional variant influencing scleroderma susceptibility at the DNASE1L3 locus; a missense polymorphism rs35677470 in DNASE1L3, with an odds ratio of 2.35 (P = 2.3 × 10⁻¹⁰) in anti-centromere antibody (ACA) positive cases.

Conclusions

This pilot study has confirmed previously reported scleroderma associations, revealed further genetic overlap between scleroderma and systemic lupus erythematosus, and identified a putative novel scleroderma susceptibility locus.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0438-8) contains supplementary material, which is available to authorized users.

Unexpected post-mortem diagnosis of systemic sclerosis presenting as pneumatosis intestinalis: revised diagnostic criteria and medicolegal implications

Systemic sclerosis is a challenging diagnosis for clinicians and pathologists alike due to its protean manifestations and often insidious onset, particularly in cases without significant titres of auto-antibodies. Herein we present a case of a female in her sixties who died rapidly following a clinical diagnosis of pneumatosis intestinalis and respiratory failure of unclear etiology. Recently revised clinical diagnostic criteria were applied to the clinical history and postmortem findings to reach an unexpected diagnosis of systemic sclerosis. The diagnosis of systemic sclerosis at autopsy has important medicolegal implications largely related to premature death due to delayed treatment or poor post-operative outcome. Moreover, familial clustering of this disease underscores the importance of maintaining a high index of suspicion in the postmortem setting.

The role of genetics and epigenetics in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a complex autoimmune disease of unclear aetiology. A multitude of genetic studies, ranging from candidate-gene studies to genome-wide association studies, have identified a large number of genetic susceptibility factors for SSc and its clinical phenotypes, but the contribution of these factors to disease susceptibility is only modest. However, in an endeavour to explore how the environment might affect genetic susceptibility, epigenetic research into SSc is rapidly expanding. Orchestrated by environmental factors, epigenetic modifications can drive genetically predisposed individuals to develop autoimmunity, and are thought to represent the crossroads between the environment and genetics in SSc. Therefore, in addition to providing a comprehensive description of the current understanding of genetic susceptibility underlying SSc, this Review describes the involvement of epigenetic phenomena, including DNA methylation patterns, histone modifications and microRNAs, in SSc.

Diagnostic and clinical significance of anti-centromere antibodies in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune disease of the liver characterised by biochemical evidence of cholestasis, elevated alkaline phosphatase levels and the presence of the highly disease specific anti-mitochondrial autoantibodies. Extra-hepatic autoimmune manifestations are common, including rheumatic disorders, such as systemic sclerosis (SSc). Notably, PBC is the most frequent autoimmune liver disease in SSc patients. Based on skin lesion extension, two major SSc disease subgroups are recognised: limited cutaneous SSc (lSSc) and diffuse cutaneous SSc. Anti-centromere antibody (ACA) positivity is highly characteristic of SSc, with up to 90% prevalence in lSSc patients. ACA has also been found in up to 30% of PBC patients and 80% of patients with a PBC/SSc overlap syndrome. The diagnostic and clinical significance of ACA positivity in patients with PBC without SSc has recently been under investigation, with several studies highlighting links to severe bile duct injury and portal hypertension. This review discusses the diagnostic and clinical relevance of ACA in patients with PBC, with or without SSc.

Genetics of systemic sclerosis: an update

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, immune cell activation, and fibrosis of the skin and internal organs. Over the past few years, a role for genetics in the susceptibility for SSc has been established. This review aims to provide an update on the progress made in the past year or so within the field of SSc genetics research. This year has been of particular interest due to the publication of a large genome-wide association study, further investigations into gene-gene interactions, and the tendency to validate genetic results in functional models.

Transforming growth factor signalling: a common pathway in pulmonary arterial hypertension and systemic sclerosis

Pulmonary arterial hypertension (PAH) is a clinical condition characterised by the presence of precapillary pulmonary hypertension (PH). Included within the subcategorisation of PAH are heritable (HPAH) and PAH associated various conditions (APAH) including systemic sclerosis (SSc). The pathogenesis of HPAH and SSc has been linked to both a genetic predisposition and epigenetic factors. TGF-β superfamily signalling has also been implicated in the development of these conditions. In this review, we discuss the role of genetic predisposition, epigenetic factors along with dysregulation in TGF-β superfamily signalling in the pathogenesis of PAH and SSc.

Familial Autoimmunity in Systemic Sclerosis — Results of a French-based Case-Control Family Study

Objective.

To assess the prevalence of autoimmune diseases in first-degree relatives of patients with systemic sclerosis (SSc), and to compare those results with control families in order to identify patterns of autoimmune diseases in relatives.

Methods.

A retrospective case-control postal questionnaire survey was performed in France to recruit patients with SSc belonging to an association of patients with SSc and unrelated age-matched and sex-matched controls. Each participant was asked to self-report on the existence of autoimmune diseases in their first-degree relatives. The prevalence of autoimmune diseases in the families of patients with SSc was compared with the corresponding prevalence in the families of controls.

Results.

A total of 121 families out of 373 (32.4%) with a member having SSc reported at least 1 autoimmune disease in 1 or more first-degree relatives. The most frequent autoimmune diseases in SSc families when adjusted for family size were autoimmune thyroid disease (AITD; 4.9%), rheumatoid arthritis (4.1%), psoriasis (3.9%), and type 1 diabetes mellitus (2.9%). Compared with control families, AITD and connective tissue diseases (SSc, systemic lupus erythematosus, or Sjögren’s syndrome) were more likely to occur in families with SSc (p = 0.01 and p = 0.01, respectively), with OR of 3.20 (95% CI 1.25–8.18) and 5.20 (95% CI 1.22–21.8). In contrast, inflammatory bowel disease was less likely to occur within families with SSc (p = 0.02, OR 0.29, 95% CI 0.11–0.80). In addition, the coexistence of more than 1 autoimmune disease in the index SSc case was associated with familial aggregation of autoimmune diseases.

Conclusion.

Our results show that autoimmune diseases cluster within families of patients with SSc. This supports the notion that these diseases might arise on a shared genetic basis underlying several autoimmune phenotypes.

Deciphering the genetic background of systemic sclerosis

Systemic sclerosis (SSc) is a severe autoimmune connective tissue disease. Over the years, evidence for a genetic background of SSc susceptibility has clearly accumulated. This article aims to provide an extensive overview of genetics in SSc research. We discuss indicators for a genetic component present in SSc, family studies, chromosomal aberrances, the involvement of the HLA region and multiple candidate genes and, finally, genome-wide association studies.

Pathogenesis of pulmonary fibrosis in systemic sclerosis: lessons from interstitial lung disease

Interstitial lung disease is a frequent complication of systemic sclerosis and currently is the leading cause of death. Our ability to predict which individuals are at greatest risk of developing clinically significant, progressive interstitial lung disease remains inadequate. Identification of circulating autoantibodies and other biomarkers, as well as genetic polymorphisms and aberrant gene expression, all hold promise as diagnostic and prognostic tools, as well as therapeutic targets. Many practice patterns for the diagnosis and monitoring of connective tissue disease-associated interstitial lung disease are based upon published experience with idiopathic interstitial lung diseases. Although there are likely commonalities in the pathophysiologic mechanisms and clinical progression among all fibrosing lung diseases, a better understanding of features unique to systemic sclerosis-associated interstitial lung disease is essential to the development of more effective monitoring and treatment strategies.

Heritability of vasculopathy, autoimmune disease, and fibrosis in systemic sclerosis: a population-based study

OBJECTIVE

To investigate the familiality of systemic sclerosis (SSc) in relation to Raynaud's phenomenon (RP) (a marker of vasculopathy), other autoimmune inflammatory disease, and fibrotic interstitial lung disease (ILD).

METHODS

A genealogic resource, the Utah Population Database (UPDB), was used to test heritability of RP, other autoimmune disease, and ILD. Diseases were defined by International Classification of Diseases, Ninth Revision codes and identified from statewide discharge data, the University of Utah Health Science Center Enterprise Data Warehouse, and death certificates and were linked to the UPDB for analysis. Familial standardized incidence ratio (FSIR), relative risks (RRs) to first-, second-, third-, and fourth-degree relatives for SSc, RP, other autoimmune disease, and ILD (with 95% confidence intervals [95% CIs]), and population attributable risk (PAR) were calculated.

RESULTS

A software kinship analysis tool was used to analyze 1,037 unique SSc patients. Fifty SSc families had significant FSIRs, ranging from 2.07 to 17.60. The adjusted PAR was approximately 8%. The RRs were significant for other autoimmune disease in the first-degree relatives (2.49 [95% CI 1.99-3.41], P = 2.42 x 10(-15)) and second-degree relatives (1.48 [95% CI 1.34-2.39], P = 0.002), for RP in first-degree relatives (6.38 [95% CI 3.44-11.83], P = 4.04 x 10(-9)) and second-degree relatives (2.39 [95% CI 1.21-4.74], P = 0.012), and for ILD in first-degree relatives (1.53 [95% CI 1.04-2.26], P = 0.03), third-degree relatives (1.47 [95% CI 1.18-1.82], P = 0.0004), and fourth-degree relatives (1.2 [95% CI 1.06-1.35], P = 0.004).

CONCLUSION

These data suggest that SSc pedigrees include more RP, autoimmune inflammatory disease, and ILD than would be expected by chance. In SSc pedigrees, genetic predisposition to vasculopathy is the most frequent risk among first-degree relatives.

LMNA, ZMPSTE24, and LBR are not mutated in scleroderma

Scleroderma is a rare multisystemic disease of unknown etiology presumed to develop in genetically predisposed patients. Since patients affected with scleroderma develop clinical features similar to those observed in some laminopathies, we decided to screen at the genomic level a cohort of 27 patients affected with either localized or systemic scleroderma for mutations in three lamin-related genes: LMNA, encoding A-type lamins; ZMPSTE24, encoding a protease involved in lamin A processing; and LBR, encoding the lamin B receptor. No mutation was retrieved, whereas 25 polymorphic sequence variations were identified, 7 of which were unreported. Functional analyses performed for three of these allowed exclusion of an impact on splicing. Multiplex ligation-dependent probe amplification analysis showed no LMNA deletion or duplication. Altogether our results suggest that LMNA, ZMPSTE24, and LBR sequence variations are not major genetic determinants involved in scleroderma pathogenesis.

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.

Genetics and genomic studies in scleroderma (systemic sclerosis)

It currently is believed that scleroderma is a complex polygenic disease that occurs in genetically predisposed individuals who have encountered specific environment exposures and/or other stochastic factors. The nature of these genetic determinants and how they interact with environmental factors are areas of active investigation. This article discusses the evidence that supports a strong genetic link to scleroderma. These studies implicate potential pathogenetic mechanisms involved in scleroderma, which, it is hoped, may translate into clinical utility, including determination of disease risk, diagnosis, prognosis, and novel therapeutics.

Genetic factors in systemic sclerosis

A number of genetic loci have been identified that appear to be associated with systemic sclerosis (SSc; scleroderma). There is mounting evidence suggesting that these genetic associations may in fact be associated with distinct phenotypes in SSc based on autoantibody pattern rather than with SSc as a single disease entity. This may ultimately have implications for approaches to therapy as well as responses to therapy. The most promising candidate genes are those involved in pathways that lead to the vascular damage and fibrosis that are the hallmarks of this disease. There is uncertainty, however, regarding the nature of the key pathological mechanisms that link these two disease processes. Recent studies have focused on Fli1 (friend leukaemia integration 1), a transcription factor that is found in immune cells, fibroblasts, and endothelial cells that regulates collagen gene function and angiogenesis. Fli1 is dysregulated in SSc skin and dermal blood vessels, and appears to play a pathological role in SSc skin fibrosis and vessel degeneration. Whether this dysregulation is due to genetic polymorphisms in the Fli1 pathway or to epigenetic mechanisms is not clear.

Clinical, immunologic, and genetic features of familial systemic sclerosis

OBJECTIVE

To examine whether the affected first-degree relatives within multicase systemic sclerosis (SSc; scleroderma) families are concordant for autoantibody profile, disease type, and HLA class II haplotypes and whether clinical expression and serologic characteristics of familial SSc differ from those of sporadic SSc.

METHODS

Seven hundred ten SSc families from the Scleroderma Family Registry and DNA Repository (Scleroderma Registry) were examined, and 18 multicase families were identified. SSc cases and their first-degree family members underwent serologic testing for different autoantibodies. The disease type and various disease features were abstracted from the available medical records. Additionally, HLA class II typing was performed on the multicase SSc sibpairs.

RESULTS

The observed SSc-specific antibody concordance within each multicase SSc family was statistically more common than expected by chance alone (P = 0.007). The autoantibody profile and disease features of familial and sporadic SSc cases did not differ significantly. The frequency of autoantibody positivity was not different between unaffected first-degree family members of patients from multicase versus singleton SSc families. HLA haplotype sharing between SSc sibpairs was significantly more common than expected (P = 0.011).

CONCLUSION

The affected members within multicase SSc families tend to be concordant for SSc-specific autoantibodies and HLA haplotypes; familial SSc does not appear to be a unique disease subset.

Systemic sclerosis in childhood: clinical and immunologic features of 153 patients in an international database

OBJECTIVE

To determine the clinical and immunologic features of systemic sclerosis (SSc) in a large group of children and describe the clinical evolution of the disease and compare it with the adult form.

METHODS

Data on 153 patients with juvenile SSc collected from 55 pediatric rheumatology centers in Europe, Asia, and South and North America were analyzed. Demographic, clinical, and immunologic characteristics of children with juvenile SSc at the onset, at diagnosis, and during the disease course were evaluated.

RESULTS

Raynaud's phenomenon was the most frequent symptom, followed by skin induration in approximately 75% of patients. Musculoskeletal symptoms were present in one-third of patients, and the most frequently involved internal organs were respiratory and gastrointestinal, while involvement of renal, cerebral, and cardiovascular systems was extremely rare. Antinuclear antibodies were present in the sera of 81% of patients. Anti-topoisomerase I (Scl-70) and anticentromere antibodies were found to be positive in 34% and 7.1% of patients, respectively. Involvement of the respiratory, gastrointestinal, and cardiovascular systems was more frequent and occurred earlier in patients who died than in those who survived. Compared with the adult form, juvenile SSc appears to be less severe, with the involvement of fewer internal organs, particularly at the time of diagnosis, and has a less characterized immunologic profile.

CONCLUSION

This study provides information on the largest collection of patients with juvenile SSc ever reported. Juvenile SSc appears to be less severe than in adults because children have less internal organ involvement, a less specific autoantibody profile, and a better long-term outcome.

Scleroderma in South Australia: further epidemiological observations supporting a stochastic explanation

The aim of this study was to determine the incidence, prevalence, survival and selective demographic characteristics of scleroderma occurring in South Australia over the 10-year period 1993-2002. Analysis of the database of the South Australian Scleroderma Register: a population-based register established in 1993. Patients with scleroderma resident in South Australia (n = 353 at 2002) were ascertained from multiple sources and clinical and demographic data were obtained from mailed questionnaire and from review of computerized hospital databases, case notes or referring letters. Time-space cluster analysis was carried out according to the Knox method. Control data were obtained from the Australian Bureau of Statistics census. The mean prevalence was 21.4 per 10(5) (95% confidence interval 20.2-22.6) and the mean cumulative incidence of 1.5 per 10(5) (95% confidence interval 1.32-1.73) with no significant change in incidence over the study period (P = 0.13). Cumulative survival improved over the study period, with patients with diffuse disease having significantly reduced survival (as compared with limited disease, P < 0.001). The proportion with diffuse disease ( approximately 22%) remained steady. There was a small but significant predisposition in patients with a continental European birthplace (P < 0.001). A family history of scleroderma was noted in 1.6% with lambda1 (familial risk) of 14.3 (95% confidence interval 5.9-34.5). However, a family history of systemic autoimmunity (especially rheumatoid arthritis) was more common (6%). No socioeconomic stratification, temporal clustering nor spatio-temporal clustering was observed either at time of initial symptom or at 10 years before disease onset. Scleroderma occurs relatively infrequently in South Australia with no significant change in incidence observed over the 10-year study period. However, cumulative survival has improved. Identified risk factors include family history of scleroderma (risk approximately 14-fold), female sex (risk approximately 5-fold) and European birthplace (risk approximately 2.5-fold); however, the majority of the disease variance appears unexplained. A stochastic explanation based on genetic instability is favoured to explain this paradox.

A polymorphism in the promoter region of the CD86 (B7.2) gene is associated with systemic sclerosis

Systemic sclerosis (SSc) is a connective tissue disease of unknown aetiology characterized by fibrosis of the skin and internal organs, vascular abnormalities and humoral autoimmunity. Strong T-cell-dependent autoantibody and HLA associations are found in SSc subsets. The co-stimulatory molecule, CD86, expressed by antigen-presenting cells, plays a crucial role in priming naïve lymphocytes. We hypothesized that SSc, or one of the disease subsets, could be associated with single-nucleotide polymorphisms of the CD86 gene. Using sequence specific primer-polymerase chain reaction (SSP-PCR) methodology, we assessed four CD86 polymorphisms in 221 patients with SSc and 227 healthy control subjects from the UK. Haplotypes were constructed by inference and confirmed using PHASE algorithm. We found a strong association between SSc and a specific haplotype (haplotype 5), which was more prevalent in patients than in controls (29% vs 15%, OR = 2.3, chi(2) = 12, P = 0.0005). This association could be attributed to the novel -3479 promoter polymorphism; a significant difference was observed in the distribution of the CD86 -3479 G allele in patients with SSc compared to controls (43.7% vs. 32.4%, OR = 1.7, chi(2) = 12.1, P = 0.0005). TRANSFAC analyses suggest that the CD86-3479T allele contains putative GATA and TBP sites, whereas G allele does not. We assessed the relative DNA protein-binding activity of the -3479 polymorphism in vitro using electromobility gel shift assays (EMSA), which showed that the -3479G allele has less binding affinity compared to the T allele for nuclear proteins. These findings highlight the importance of co-stimulatory pathways in SSc pathogenesis.

Endothelin axis polymorphisms in patients with scleroderma

OBJECTIVE

To evaluate the distribution of polymorphisms in the endothelin 1 (EDN1), endothelin receptor A (EDNRA) and endothelin receptor B (EDNRB) genes in systemic sclerosis (SSc; scleroderma) and SSc subsets.

METHODS

Two hundred five patients with SSc and 255 healthy controls were screened for polymorphisms in EDN1, EDNRA, and EDNRB, using sequence-specific primer-polymerase chain reaction. The polymorphisms studied were at the following positions: for EDN1, -1370 (T-1370G) of the promoter, +138 of exon 1 (+138 A/-), +85 of exon 3 (E106E), and +23 of exon 5 (K198N); for EDNRA, -231 of exon 1 (G-231A), and +69(H323H) and +105 (E335E) of exon 6; for EDNRB, +2841 of exon 2 (EDNRB-3), -2547 of exon 3 (EDNRB-2), and -2446 of exon 3 (EDNRB-1).

RESULTS

No significant differences between the SSc group as a whole and control subjects were observed for any of the investigated polymorphisms in EDN1, EDNRA, and EDNRB. However, compared with patients with limited cutaneous SSc, patients with diffuse skin involvement had an increased frequency of allele carriage of EDNRB-1A (76.8% versus 54.4%; P = 0.002), EDNRB-2A (79.7% versus 60.2%; P = 0.006), and EDNRB-3G (79.7% versus 56.6%; P = 0.001). Significantly increased carriage frequencies for EDNRA alleles H323H/C and E335E/A were observed in SSc patients with anti-RNA polymerase (anti-RNAP) antibodies, compared with both anti-RNAP-negative SSc patients (P < 0.05) and control subjects (P < 0.005).

CONCLUSION

The finding of associations between endothelin receptors A and B and distinct clinical and immunologic SSc subsets supports the role of endothelin and its receptors in the pathogenesis of SSc. However, these findings and their functional significance need to be confirmed and investigated in future studies.

Genetics and proteomics in scleroderma

The pathogenesis of systemic sclerosis (SSc; scleroderma) is still enigmatic. Genetic, familial, and twin studies suggest that SSc occurs in genetically susceptible individuals. Recent high-throughput technologies, including gene expression profiling and proteomics, have accelerated the rate of information acquired on possible mechanisms involved in SSc pathogenesis. The potential of the data obtained lies in their use for identifying new disease markers, monitoring disease activity, and developing tailored therapies. The result is an era of unprecedented advance that will benefit SSc and many other diseases.

Gender issues in pulmonary vascular disease

Gender differences in pulmonary vascular diseases, as exemplified by primary pulmonary hypertension and scleroderma-related pulmonary hypertension, are not well-explained; however, in general terms, they seem to be related to a combination of genetic predispositions and gender-specific environmental triggers. More information is needed in both areas with respect to mechanisms of disease. More information also is needed about possible gender differences in disease presentation,course, and response to treatments.

Systemic sclerosis: the susceptible host (genetics and environment)

It is becoming evident that several genetic factors participate in modulating susceptibility to SSc and its clinical manifestations. Some genes that specifically affect ECM metabolism and vascular function may be unique to SSc and scleroderma-related disorders; others, such as those genes involved in regulating immune tolerance, are likely shared with other autoimmune diseases. The effect of genetic variations (or polymorphisms) that are found in most of these genes taken individually will likely have only a small or modest effect on disease risk; only a few genetic variations are expected to be highly penetrant. Moreover, genetic studies in SSc have to deal with the additional issues of heterogeneous phenotypes, low disease prevalence in the general population, and an even greater paucity of multiplex families that makes traditional linkage studies difficult, if not impossible. Alternative approaches include allelic association studies, but conventional case-controls designs may be subject to selection bias and will require large sample sizes if the genes that are under investigation confer only modest (OR = 1.5-2.0) disease risk (Fig. 2). The simultaneous examination of several genes that are biologically relevant to a specific disease process to attain higher aggregate ORs, is one approach that was used in several reports that were cited in this review. The use of family-based controls, such as in the transmission-disequilibrium test (based on assessment of the transmitted or nontransmitted alleles that are associated with disease from heterozygous parents to affected offspring), would provide more robustness to spurious associations from population stratification, but is actually less powerful and efficient than case-control designs. Furthermore, for many late adult-onset diseases the effort required to obtain samples from living parents are for a variety of reasons not trivial. The success of these allelic association-based approaches depends on the identification of likely candidate disease genes (or at least markers in disequilibrium with disease genes), careful definition/ascertainment of disease phenotypes to minimize genetic heterogeneity, and for case-control designs, strategies to account for population stratification or admixture. The identification of candidate genes will be aided by rapid progress in the Human Genome Project and other genome efforts that will eventually identify all human genetic variations. Although this will lead to better understanding of the genes that might be involved in complex diseases, much work is required to understand the basic biology of how disease genotypes become clinical phenotypes. This is especially daunting in complex diseases, such as SSc, where the phenotype (including disease susceptibility and clinical presentation) is influenced by dynamic interactions between genetic variations and environment. Multi-center collaborative efforts with research paradigms that integrate genetic and environmental factors (including sociodemographic variables) will be required to elucidate the contribution of environment and genetics in the pathogenesis of SSc.

Scleroderma epidemiology

Evidence from multiple sources indicates that SSc does not occur randomly in the population; there are particular groups who are at greater risk. The overall incidence rate of SSc in the adult population of the United States is approximately 20 per million per year; this rate has increased from 1944 to 1973, but has been relatively stable since that time. The prevalence of SSc in the United States also seems to be stable over the past two decades with a prevalence estimate for adults of 240 per million. Recent population studies suggest that SSc occurs more frequently in the United States than in continental Europe, the United Kingdom, and in some areas in Asia. Overall survival has improved over the past few decades; mean survival is approximately 12 years from diagnosis. Renal disease accounts for some of the early mortality, but pulmonary disease has emerged as a major cause of death. Cardiac disease is also correlated with a poorer prognosis. Gastrointestinal involvement contributes to morbidity and, indirectly, to mortality, but the magnitude of this contribution is difficult to assess. Women are affected more frequently than men but the factors that are responsible for this are not apparent. Studies of reproductive history have provided conflicting data; some studies suggested that the number of pregnancies may influence later disease expression, whereas other studies found no correlation. Racial factors seem to play a role in disease susceptibility, as well as disease expression. Age-specific incidence rates are higher in black women than in white women; the greatest difference occurs in the young to middle adult age group (less than 54 years of age). Diffuse disease also seems to occur more commonly in the black population than in the white. Age at onset of diffuse disease is younger, on average, than the age at onset of limited disease; age-adjusted survival is worse in black women than in white women because of their predilection for diffuse disease. Reports of geographic clustering are intriguing; the reported clusters in London and Italy have not resulted in the identification of potential causal factors. The Choctaw Native American cluster suggests that genetic factors that have not been identified may play an important role. Familial clustering of SSc has been demonstrated in the United States and in Australia, which provides additional evidence of a genetic component. It is likely that there is a strong interplay among genetic factors, hormonal or reproductive-related events, and an external trigger that must interact to result in clinical disease.

[Systemic sclerosis and pregnancy]

PURPOSE

Pregnancy in a patient with systemic sclerosis (SSc) may pose a double problem to the medical team: influence of SSc on pregnancy and consequences of pregnancy to SSc manifestations.

CURRENT KNOWLEDGE AND KEY POINTS

Concepts have evolved. SSc was considered for a long time not only as not very propitious for pregnancy but also as a strict contraindication for procreation because risks for the mother and the baby were thought to be major. Currently, fertility is thought to be normal. Miscarriages and small-for-gestation age infants rate do not seem to be higher in SSc. Maternal and perinatal mortality is also not higher in SSc without severe visceral manifestations, i.e. without either pulmonary hypertension, or cardiac or respiratory insufficiency. Conversely, there is a significantly higher frequency of premature infants in SSc. As regards influence of pregnancy on SSc, the greatest fear is the occurrence of renal crisis, which may be life threatening for both mother and child. Each elevation of blood pressure, even if this increase is mild, should be considered as potentially very serious. However, pregnancy itself does not seem to increase the risk of renal crisis. Consequences of pregnancy to SSc manifestations are various but usually mild.

FUTURE PROSPECTS AND PROJECTS

SSc is not a strict contraindication for pregnancy only if severe organ involvement, diffuse subset of SSc or recent onset of the disease has been ruled out. Physicians should be aware of specific problems, which SSc is possibly posing during pregnancy. Finally, it has been recently suggested that pregnancies could be involved in the pathogenesis of SSc through persisting microchimerism of fetal origin.

The genetics of systemic sclerosis

The etiopathogenesis of systemic sclerosis (SSc) is unclear. With no definitive evidence supporting an environmental cause, recent attention has focused on genetic factors. Familial clustering and ethnic influences have been demonstrated. Human leukocyte antigen (HLA) associations exist but are more related to the presence of particular autoantibodies rather than to the disease. In addition, no single major histocompatibility complex (MHC) allele predisposes to SSc in all ethnic groups. The role of microchimerism in SSc is a novel yet unproven hypothesis that may be related to intergenerational HLA compatibility. Recent studies investigating polymorphisms in genes coding for extracellular matrix proteins and cell-signaling molecules implicate non-MHC areas in SSc pathogenesis. The data reviewed suggest that SSc is a multigenic complex disorder.

Genetic epidemiology: systemic sclerosis

Systemic sclerosis (SSc) is a multisystem connective tissue disease characterised phenotypically by fibrosis and ischaemic atrophy. Its aetiology is most likely multifactorial. A genetic predisposition to the condition is suggested by reports of familial SSc (a positive family history is the strongest risk factor yet identified), by animal models, and by disease-association studies, in which researchers have examined a wide variety of genes including those involved in fibrosis, in vascular function and structure, and in autoimmunity - the relative rarity of SSc has precluded linkage studies, except in the Choctaw Indians. Recent advances in genetic methodologies should further our understanding of this complex disease process.

Familial occurrence frequencies and relative risks for systemic sclerosis (scleroderma) in three United States cohorts

OBJECTIVE

To determine the frequency with which scleroderma (systemic sclerosis; SSc) recurs in families and the familial relative risk (lambda) in the US.

METHODS

Family histories of SSc were prospectively surveyed in 3 large US cohorts of SSc patients, 2 in Texas and 1 in Michigan. Diagnoses of familial SSc were verified by rheumatologist evaluation and/or review of medical records. Familial relative risks for first-degree relatives (lambda1) and siblings (lambdas) were calculated using actual reported counts of first-degree relatives in 2 cohorts and recent estimates of SSc prevalence in the US.

RESULTS

Compared with the estimated prevalence of SSc in the US (2.6 cases/10,000 population [0.026%]), the disease occurred in 1 or more first-degree relatives in 1.5-1.7% of SSc families in the 3 cohorts (or 11 of 703 families [1.6%]), a significant increase. Familial relative risks in first-degree relatives in the 3 cohorts ranged from 10 to 16 (13 combined), and in siblings they ranged from 10 to 27 (15 combined).

CONCLUSION

SSc occurs significantly more frequently in families with scleroderma (1.6%) than in the general population (0.026%). A positive family history of SSc is the strongest risk factor yet identified for SSc; however, the absolute risk for each family member remains quite low (<1%).

Scleroderma in South Australia: epidemiological observations of possible pathogenic significance

BACKGROUND

Scleroderma is an autoimmune disorder of unknown cause. Previous epidemiological studies have suggested some regional clustering and associations with occupations involving exposure to silica dusts and hydrocarbons.

AIMS

To determine: (i) prevalence and incidence of scleroderma in South Australia (SA), a state with a stable population living in well-defined urban, rural and industrial regions, (ii) hospital separation rates, (iii) cumulative survival rates, (iv) gender and disease subclassification, (v) geographical residency and occupations, (vi) familial associations and (vii) age at onset versus age-specific incidence rate.

METHODS

Creation of the South Australian Scleroderma Register (SASR) to identify demographics and clinical and serological features of all scleroderma patients resident in SA.

RESULTS

Scleroderma occurs in South Australia with a point prevalence of 23 per 10(5) and an incidence of approximately 1/15th of this. However, this prevalence is high compared with other regional world studies. Scleroderma is predominantly a female disease, with most patients having the limited form of scleroderma characterized by the presence of the anticentromere antibody and a mean survival of 27.6 years. In contrast, diffuse scleroderma is a less benign disease occurring at an early age of onset and has a mean survival of 9.6 years. Scleroderma occurs throughout SA without regional localization. Weak associations are seen in males, but not females, with occupations involving possible environmental exposure to silica or hydrocarbons. Scleroderma rarely occurs in families.

CONCLUSION

No strong genetic or environmental influences were found to account for the relatively common occurrence of scleroderma in SA. The age at onset versus age-specific incidence curve suggests that scleroderma can be considered as a stochastic illness involving a number of random events occurring in a predisposed population. These random events may involve mutations of pivotal somatic genes.

Localized and systemic scleroderma

Scleroderma is a broad term encompassing both localized and systemic sclerosis. Localized scleroderma is a cutaneous limited fibrosis that manifests as plaque morphea, generalized morphea, linear scleroderma, and deep morphea. Systemic scleroderma (sclerosis) can manifest as either limited or diffuse disease. Limited systemic sclerosis is typically preceded by Raynaud's phenomenon, involves cutaneous sclerosis distal to the elbows, with gastrointestinal and pulmonary fibrosis, and anticentromere antibody positivity. Diffuse systemic scleroderma is characterized by simultaneous Raynaud's phenomenon, cutaneous skin involvement proximal to the elbow with gastrointestinal, pulmonary, renal and cardiac fibrosis, and positive serology for antitopoisomerase and anti-RNAP III antibodies. This article discusses the classification, epidemiology, pathogenesis, clinical manifestations, treatment, and prognosis of the scleroderma.