Genetic risk and protective factors for idiopathic inflammatory myopathy in Koreans and American whites: a tale of two loci

Incidence, Prevalence, and Mortality of Dermatomyositis: A Population-Based Cohort Study

OBJECTIVE

We aimed to determine the population-based incidence, prevalence, and mortality of dermatomyositis (DM) using European Alliance of Associations for Rheumatology (EULAR)/American College of Rheumatology (ACR) criteria.

METHODS

This population-based cohort study included incident DM from January 1, 1995 to December 31, 2019. We manually reviewed all individuals with at least 1 code for DM or polymyositis to determine if they met EULAR/ACR criteria, subspecialty physician diagnosis, and/or Bohan and Peter criteria. We age- and sex-adjusted incidence and prevalence estimates to the US non-Hispanic White year 2000 population and estimated prevalence on January 1, 2015. Standardized mortality ratios (SMRs) with 95% confidence intervals (95% CIs) compared observed to expected mortality adjusting for age, sex, and year.

RESULTS

We identified 40 cases of verified DM, with 29 cases incident in Olmsted County from 1995 to 2019. The mean age was 57 years, 26 (90%) were female, and 12 (41%) had clinically amyopathic DM (CADM). The median follow-up time was 8.2 years. The overall adjusted incidence of DM was 1.1 (95% CI 0.7-1.5) per 100,000 person-years, and prevalence was 13 (95% CI 6-19) per 100,000. The SMR was significantly elevated among the myopathic DM cases (3.1 [95% CI 1.1-6.8]) but not CADM cases (1.1 [95% CI 0.2-3.3]). The positive predictive value of ≥2 DM codes was only 40 of 82 (49%).

CONCLUSION

This population-based study found that DM incidence and prevalence were higher than previously reported. Mortality was significantly elevated for myopathic DM but not for CADM.

Beyond Titer: Expanding the Scope of Clinical Autoantibody Testing

Background

Autoantibodies that bind self-antigens are a hallmark of autoimmune diseases, but can also be present in healthy individuals. Clinical assays that detect and titer antigen-specific autoantibodies are an important component of the diagnosis and monitoring of autoimmune diseases. Autoantibodies may contribute to disease pathogenesis via effector functions that are dictated by both the antigen-binding site and constant domain.

Content

In this review, we discuss features of antibodies, in addition to antigen-binding specificity, which determine effector function. These features include class, subclass, allotype, and glycosylation. We discuss emerging data indicating that analysis of these antibody features may be informative for diagnosis and monitoring of autoimmune diseases. We also consider methodologies to interrogate these features and consider how they could be implemented in the clinical laboratory.

Summary

Future autoantibody assays may incorporate assessment of additional antibody features that contribute to autoimmune disease pathogenesis and provide added clinical value.

Efficacy and safety of statins in ethnic differences: a lesson for application in Indigenous Australian patient care

Although statins are effective in treating high cholesterol, adverse effects do occur with their use. Efficacy and tolerability vary among statins in different ethnic groups. Indigenous Australians have a high risk for cardiovascular and kidney diseases. Prescribing statins to Indigenous Australians with multi-morbidity requires different strategies to increase efficacy and reduce their toxicity. Previous studies have reported that Indigenous Australians are more susceptible to severe statin-induced myopathies. However, there is a lack of evidence in the underlying genetic factors in this population. This review aims to identify: inter-ethnic differences in the efficacy and safety of statins; major contributing factors accounting for any identified differences; and provide an overview of statin-induced adverse effects in Indigenous Australians.

Prevalence of interstitial lung disease in polymyositis and dermatomyositis: A meta-analysis from 2000 to 2020

OBJECTIVE

Interstitial lung disease (ILD) is the most important prognostic factor for mortality in patients with polymyositis (PM) and dermatomyositis (DM), but the prevalence of ILD in PM/DM may vary between countries. The aim of this study was to determine the overall prevalence of ILD in global patients with PM/DM.

METHODS

We performed a systematic literature review of studies published from Jan 1, 2000 to April 30, 2020 on ILD and PM/DM. We extracted data and pooled the prevalence by using a random-effect model due to high heterogeneity. Heterogeneity was assessed by subgroup analysis and sensitivity analysis.

RESULTS

A total of 34 studies with 10,130 patients were included in our meta-analysis. Pooled data demonstrated that the global prevalence of ILD in patients with PM/DM was 0.41 (95% confidence interval [CI] 0.35-0.48). However, this prevalence varied with geographical locations and time trends. The prevalence of ILD in PM/DM was 0.5 (95% CI 0.42-0.57) in Asia, 0.23 (95% CI 0.15-0.31) in America, and 0.26 (95% CI 0.18-0.34) in Europe. A higher prevalence of ILD was reported in studies published in 2011-2015 (0.43, 95% CI 0.34-0.52) and 2016-2020 (0.45, 95% CI 0.35-0.54), compared with those published in 2000-2010 (0.27, 95% CI 0.16-0.39). The pooled prevalence of ILD in patients with DM, PM, and clinically amyopathic dermatomyositis subtype was 0.42 (95% CI 0.35-0.49), 0.35 (95% CI 0.27-0.42), and 0.53 (95% CI 0.32-0.74), respectively. Patients with anti-Jo-1 and anti-melanoma differentiation-associated gene 5 antibodies were more likely to develop ILD than other myositis-specific autoantibodies.

CONCLUSION

The global prevalence of ILD in patients with PM/DM was approximately 41% and the condition was predominant in Asians. This highlights potential genetic and environmental differences in the pathogenesis of ILD in patients with PM/DM. More studies are required to elucidate the specific associations.

Incidence, survival, and risk of cardiovascular events in adult inflammatory myopathies in South Korea: a nationwide population-based study

OBJECTIVE

Epidemiological studies on inflammatory myopathies (IMs) show widely variable results, and studies on Asians are lacking. Despite emerging interest in the cardiovascular disease (CVD) risk associated with IMs, the prevalence of CVD in IM patients and its impact on mortality remain unclear. We conducted a nationwide, population-based study on the incidence, mortality, and associated major CVD events of IMs in the Republic of Korea over 11 years.

METHOD

Using the nationwide, population-based National Health Insurance claims database and the Rare Intractable Disease registration programme, we estimated incidence, mortality, and CVD occurrence. Survival was examined using the Kaplan-Meier method. Mortality rate in IMs with CVD was analysed by Cox proportional hazards regression.

RESULTS

There were 3014 incident cases, 640 of whom died during the study period. The mean annual incidence was 7.16/10⁶. Dermatomyositis (DM) and polymyositis (PM) had 5 year survival rates of 76.8% and 79.3%, respectively. Cardiovascular events occurred in 155 patients and 40.6% of IM patients with CVD died. Acute myocardial infarction in men had the highest risk of any CVD event in both DM [standardized incidence ratio (SIR) 4.2, 95% confidence interval (95% CI) 2.4-7.2] and PM (SIR 3.5, 95% CI 1.8-7.0). Haemorrhagic stroke had the highest hazard ratio (HR) in both DM (HR 2.31, 95% CI 1.13-4.70) and PM patients (HR 2.10, 95% CI 1.03-4.27) compared with the general population with CVD.

CONCLUSION

We found persistently low incidence, poor survival, and high major CVD incidence in IMs, and increased mortality in IMs with CVD.

Polymyositis and dermatomyositis - challenges in diagnosis and management

Polymyositis (PM) and dermatomyositis (DM) are different disease subtypes of idiopathic inflammatory myopathies (IIMs). The main clinical features of PM and DM include progressive symmetric, predominantly proximal muscle weakness. Laboratory findings include elevated creatine kinase (CK), autoantibodies in serum, and inflammatory infiltrates in muscle biopsy. Dermatomyositis can also involve a characteristic skin rash. Both polymyositis and dermatomyositis can present with extramuscular involvement. The causative factor is agnogenic activation of immune system, leading to immunologic attacks on muscle fibers and endomysial capillaries. The treatment of choice is immunosuppression. PM and DM can be distinguished from other IIMs and myopathies by thorough history, physical examinations and laboratory evaluation and adherence to specific and up-to-date diagnosis criteria and classification standards. Treatment is based on correct diagnosis of these conditions.

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Challenges of diagnosis and management influences the clinical research and practice of Polymyositis and dermatomyositis.

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Diagnostic criteria have been updated and novel therapies have been developed in PM/DM.

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Pathogenesis investigation and diagnosis precision improvement may help to guide future treatment strategies.

Human leukocyte antigen in Japanese patients with idiopathic inflammatory myopathy

Objective: The human leukocyte antigen (HLA) is the strongest genetic risk factor for idiopathic inflammatory myopathy (IIM), and different HLA alleles have been reported to be associated with IIM susceptibility among different ethnic groups. In this study, we have investigated HLA alleles associated with IIM in Japanese patients.Methods: Genotyping of HLA-DRB1 and DPB1 were performed in 252 Japanese IIM patients (166 dermatomyositis [DM] and 86 polymyositis [PM] patients) and the association was analyzed with comparison to controls (n = 1026 for DRB1 and n = 413 for DPB1).Results: DRB1*08:03 was associated with IIM (p = 1.60 × 10^-5, pc = .0005, odds ratio [OR] 2.11, 95% confidence interval [CI] 1.52-2.92) and DM (p = .0004, pc = .0128, OR 2.06, 95%CI 1.40-3.02). DPB1*05:01 was also associated with IIM (p = .0001, pc = .0021, OR 1.96, 95%CI 1.38-2.77) and DM (p = .0005, pc = .0075, OR 2.05, 95%CI 1.37-3.08). DRB1*09:01 (p = .0012, pc = .0368, OR 0.35, 95% CI 0.18-0.69) and DPB1*04:01(p = .0004, pc = .0057, OR 0.05, 95% CI 0.00-0.85) were protectively associated with PM. Two locus analyses suggested that DRB1*09:01 and DPB1*04:01 were independently associated with PM.Conclusion: Protective associations of HLA were detected in Japanese PM patients.

Focused HLA analysis in Caucasians with myositis identifies significant associations with autoantibody subgroups

Objectives

Idiopathic inflammatory myopathies (IIM) are a spectrum of rare autoimmune diseases characterised clinically by muscle weakness and heterogeneous systemic organ involvement. The strongest genetic risk is within the major histocompatibility complex (MHC). Since autoantibody presence defines specific clinical subgroups of IIM, we aimed to correlate serotype and genotype, to identify novel risk variants in the MHC region that co-occur with IIM autoantibodies.

Methods

We collected available autoantibody data in our cohort of 2582 Caucasian patients with IIM. High resolution human leucocyte antigen (HLA) alleles and corresponding amino acid sequences were imputed using SNP2HLA from existing genotyping data and tested for association with 12 autoantibody subgroups.

Results

We report associations with eight autoantibodies reaching our study-wide significance level of p<2.9×10^–5. Associations with the 8.1 ancestral haplotype were found with anti-Jo-1 (HLA-B*08:01, p=2.28×10^–53 and HLA-DRB1*03:01, p=3.25×10^–9), anti-PM/Scl (HLA-DQB1*02:01, p=1.47×10^–26) and anti-cN1A autoantibodies (HLA-DRB1*03:01, p=1.40×10^–11). Associations independent of this haplotype were found with anti-Mi-2 (HLA-DRB1*07:01, p=4.92×10^–13) and anti-HMGCR autoantibodies (HLA-DRB1*11, p=5.09×10^–6). Amino acid positions may be more strongly associated than classical HLA associations; for example with anti-Jo-1 autoantibodies and position 74 of HLA-DRB1 (p=3.47×10^–64) and position 9 of HLA-B (p=7.03×10^–11). We report novel genetic associations with HLA-DQB1 anti-TIF1 autoantibodies and identify haplotypes that may differ between adult-onset and juvenile-onset patients with these autoantibodies.

Conclusions

These findings provide new insights regarding the functional consequences of genetic polymorphisms within the MHC. As autoantibodies in IIM correlate with specific clinical features of disease, understanding genetic risk underlying development of autoantibody profiles has implications for future research.

Predicting acute kidney injury: current status and future challenges

Acute kidney injury (AKI) is characterized by an acute decline in renal function and is associated to increased mortality rate, hospitalization time, and total health-related costs. The severity of this ‘fearsome’ clinical complication might depend on, or even be worsened by, the late detection of AKI, when the diagnosis is based on the elevation of serum creatinine (SCr). For these reasons, in recent years a great number of new tools, biomarkers and predictive models have been proposed to clinicians in order to improve diagnosis and prevent the development of AKI. The purpose of this narrative paper is to review the current state of the art in prediction and early detection of AKI and outline future challenges.

Inflammatory Myopathies with Cutaneous Involvement: from Diagnosis to Therapy

The group of idiopathic inflammatory myopathies (IIM) include various disorders of skeletal muscles with or without skin involvement. The most common types are dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM) and necrotizing autoimmune myopathy (NAM). Dermatomyositis subdivides into various clinical forms such as juvenile, amyopathic or paraneoplastic dermatomyositis, scleromyositis, overlap or anti-synthetase syndromes, etc.

Recently, numerous new antibodies defining the characteristic clinical phenotype have been described as anti-MDA5 antibodies associated with interstitial lung disease and amyopathic dermatomyositis or anti-TIF1γ antibodies as markers for paraneoplastic dermatomyositis. Moreover, new clinical entities as drug-induced dermatomyositis are presumed, since some medications may induce, or trigger inflammatory myopathies.

Knowledge of the complex methods and techniques required to diagnose the disease is of great importance in clinical practice. The variety of clinical variants needs diagnosis because of the differing prognosis and therapeutic modalities.

Clinical and Prognostic Factors Associated With Survival in Mexican Patients With Idiopathic Inflammatory Myopathies

BACKGROUND

Factors associated with survival in patients with idiopathic inflammatory myopathies are heterogeneous.

OBJECTIVE

This study aimed to describe clinical and prognostic factors associated with survival in Mexican patients with idiopathic inflammatory myopathies.

METHODS

Patients with dermatomyositis (DM) and polymyositis (PM) seen at a tertiary care center from 1985 to 2012 were included. Demographic and clinical characteristics, comorbidities, treatment, and the time to death were recorded. Patients with juvenile DM were excluded. Univariate and multivariate analyses were performed to identify factors associated with mortality.

RESULTS

A total of 264 patients with DM and 69 patients with PM were studied. Patients with DM had lower levels of creatine phosphokinase, less cumulative dose of prednisone, higher frequency of dysphagia, and no difference in frequency of interstitial lung disease compared with patients with PM. Patients with DM had lower survival during the first 4 years of disease (80%; 95% confidence interval [CI], 0.74-0.85 vs 89%; 95% CI, 0.78-0.95; P = 0.03 log-rank). Respiratory failure due to pulmonary infection was the main cause of death in patients with DM; miscellaneous causes were responsible for death in patients with PM. Muscular strength (hazard ratio [HR], 0.48; 95% CI, 0.27-0.83; P = 0.01), platelet count (HR, 0.98; 95% CI, 0.98-0.99; P = 0.002), as well as ever use of methotrexate (HR, 0.21; 95% CI, 0.07-0.65; P = 0.007) and azathioprine (HR, 0.21; 95% CI, 0.06-0.68; P = 0.009) were independent factors associated with mortality in patients with DM; in those with PM, only cancer was associated (HR, 8.0; 95% CI, 1.4-43.9; P = 0.01).

CONCLUSIONS

Patients with DM had lower survival during the first 4 years of disease than patients with PM. Factors associated with mortality differed in both groups.

Variation at HLA-DPB1 is associated with dermatomyositis in Chinese population

Dermatomyositis (DM) is a polygenic disorder characterized by inflammation of skeletal muscle and skin. To date, the exact etiopathogenesis of DM remains elusive. To explore the genetic basis of DM, we conducted genome-wide genotyping analysis of 127 patients and 1566 healthy controls by Illumina Human OmniZhongHua-8 BeadChips in the Chinese Han population. We investigated whether the three SNP (rs7750458, rs9501251 and rs9500928) at 6p21.32 in the HLA-DPB1 gene were significantly associated with DM (P < 5 × 10^-8 ) and identified two susceptibility loci at 7q34 (PIP, rs9986765, P = 7.45 × 10^-7 , odds ratio [OR] = 2.71) and 10q24.2 (CPN1, rs3750716, P = 9.04 × 10^-7 , OR = 4.39) with suggestive evidence. We imputed 6674 classical human leukocyte antigen (HLA) alleles, amino acids and SNP from the discovery dataset, and stepwise analysis revealed that HLA-DPB1*17 in class II HLA genes were significantly associated with DM susceptibility. This study represents the first genome-wide association study (GWAS) of DM in the Chinese Han population. For the first time, HLA-DPB1 was found to be associated with DM in this population. Moreover, we identified two novel suggestive susceptibility loci (PIP and CPN1) and confirmed four previously reported genes (DMB, DQA1, DQB1 and DRB1) having potential associations with DM in the Chinese Han population. Our GWAS results in this population should provide important information regarding the genetic etiopathogenesis of DM and facilitate the development of new therapies for the treatment of DM and the prevention of DM progression.

HLA class II alleles may influence susceptibility to adult dermatomyositis and polymyositis in a Han Chinese population

Background

Polymyositis (PM) and dermatomyositis (DM) are idiopathic inflammatory myopathies. Genetic variability in human leukocyte antigen (HLA) genes plays an important role in the pathogenesis of PM and DM. However, few studies on the subject in Chinese populations have been reported thus far.

Methods

We studied the influence of HLA polymorphisms on DM and PM susceptibility by analyzing HLA-DRB1, HLA-DQA1, and HLA-DQB1 alleles in 71 adult DM patients, 20 adult PM patients, and 113 controls in a Han Chinese population.

Results

A positive association was found between HLA-DQA1*0104 and DM (p = 0.01; corrected p (p_corr) NS; odds ratio (OR) = 2.58; 95% confidence interval (CI): 1.18–5.64), while an inverse correlation was noted between HLA-DQB1*0303 and myositis patients with interstitial lung inflammation (p = 0.01; p_corr NS; OR = 0.25; 95% CI: 0.07–0.73). A positive relationship was also observed between HLA-DRB1*07 and DM (p = 0.01; p_corr NS; OR = 2.26; 95% CI: 1.12–4.59), while HLA-DRB1*03 seems to be protective against DM (p = 0.01; p_corr NS; OR = 0.26; 95% CI: 0.06–0.81). The lung complication was closely associated with HLA-DRB1*04 (p = 0.01; p_corr NS; OR = 2.82; 95% CI: 1.15–6.76) and HLA-DRB1*12 (p = 0.02; p_corr NS; OR = 2.52; 95% CI: 1.02–6.07). The frequency of HLA-DRB1*07 was significantly higher among myositis patients with dysphagia than among controls (p = 0.01; p_corr NS; OR = 4.78; 95% CI: 1.03–24.42). The putative haplotype DRB1*07-DQA1*01-DQB1*02 was positively correlated with DM (p = 0.03; p_corr NS; OR = 2.90; 95% CI: 1.02–8.93) and the lung complication (p = 0.02; p_corr NS; OR = 3.45; 95% CI: 1.04–11.58).

Conclusions

Our results demonstrate that HLA alleles may be involved in susceptibility to adult DM and PM in the Han Chinese population.

Association between a C8orf13-BLK polymorphism and polymyositis/dermatomyositis in the Japanese population: an additive effect with STAT4 on disease susceptibility

Background

Accumulating evidence has shown that several non-HLA genes are involved in the susceptibility to polymyositis/dermatomyositis. This study aimed to investigate the involvement of C8orf13–BLK, one of the strongest candidate genes for autoimmune diseases, in susceptibility to polymyositis/dermatomyositis in the Japanese population. A possible gene–gene interaction between C8orf13–BLK and STAT4, which we recently showed to be associated with Japanese polymyositis/dermatomyositis, was also analyzed.

Methods

A single-nucleotide polymorphism in C8orf13–BLK (dbSNP ID: rs13277113) was investigated in the Japanese population using a TaqMan assay in 283 polymyositis patients, 194 dermatomyositis patients, and 656 control subjects.

Results

The C8orf13–BLK rs13277113A allele was associated with overall polymyositis/dermatomyositis (P<0.001, odds ratio [OR] 1.44, 95% confidence interval [CI] 1.19–1.73), as well as polymyositis (P = 0.011, OR 1.32, 95% CI 1.06–1.64) and dermatomyositis (P<0.001, OR 1.64, 95% CI 1.26–2.12). No association was observed between the C8orf13–BLK rs13277113A allele and either interstitial lung disease or anti-Jo-1 antibody positivity. The C8orf13–BLK rs13277113 A and STAT4 rs7574865 T alleles had an additive effect on polymyositis/dermatomyositis susceptibility. The strongest association was observed in dermatomyositis, with an OR of 3.07 (95% CI; 1.57–6.02) for the carriers of four risk alleles at the two SNP sites, namely, rs1327713 and rs7574865.

Conclusions

This study established C8orf13–BLK as a new genetic susceptibility factor for polymyositis/dermatomyositis. Both C8orf13–BLK and STAT4 exert additive effects on disease susceptibility. These observations suggested that C8orf13–BLK, in combination with STAT4, plays a pivotal role in creating genetic susceptibility to polymyositis/dermatomyositis in Japanese individuals.

Idiopathic inflammatory myopathies

Inflammatory myopathies are chronic, immune-mediated diseases characterised by progressive proximal muscle weakness. They encompass a variety of syndromes with protean manifestations. The diagnosis is based on Bohan and Peter's classification criteria, which nowadays seem to be obsolete. Our increasing knowledge about the risk factors, genetic susceptibility and immunological pathways in the disease mechanism leads to the establishment of a new, immunogenetically and serologically validated diagnostic criteria system. The treatment of idiopathic inflammatory myopathy is also a complex task requiring much experience. The aims of therapy are to increase muscle strength, prevent the development of contractures and manage the systemic manifestations of the disease. The most important one is the early detection of diseases and patients' immunological control in special centres. Using the basis therapeutic drugs temporary or permanent remission can be achieved, which improves patientsG' quality of life and functional ability. Rehabilitation and physiotherapy in the remission period may significantly improve the outcome of patients with functional disorders. The introduction of new biological therapies further allows us to control the myositis patients' state more effectively. The aim of this review is to summarise our knowledge about clinical symptoms, pathomechanism, as well as genetic, serologic and environmental risk factors. We would also like to present the way to diagnosis and the latest research about diagnostic criteria system, proposed outcome measures and therapeutic possibilities.

[New aspects on the pathogenesis of myositis]

Idiopathic inflammatory myopathies (IIM) are chronic inflammatory diseases of muscle characterized by proximal muscle weakness. There are three main groups of diseases, dermatomyositis, polymyositis and inclusion body myositis. The muscle tissue is invaded by the humoral autoantibody producing immune system (B-cells) and by the cellular immune system with autoaggressive and inflammation modulating cells (e.g. dendritic cells, monocytes/macrophages, CD4 + and CD8 + T-cells and natural killer cells). The presence of specific or associated autoantibodies and inflammatory cellular infiltrates with cytotoxic and immune autoreactive properties are characteristic for IIM diseases. The pathogenesis is still unknown; nevertheless, there are several hints that exogenic factors might be involved in initiation and disease progression and bacterial, fungal and viral infections are thought to be possible initiators. Up to now information on prognostic markers to help with decision-making for individual treatment are limited. In addition, there has been only limited therapeutic success including conventional or novel drugs and biologicals and comparative validation studies are needed using similar outcome measurements. Moreover, to facilitate the use and development of novel therapies, elaboration of intracellular and cell-specific regulation could be useful to understand the etiopathogenesis and allow a better diagnosis, prognosis and possibly also a prediction for individualized subgroup treatment.

Mortality factors in idiopathic inflammatory myopathy: focusing on malignancy and interstitial lung disease

OBJECTIVES

The objective of this study was to assess the incidence and common types of concomitant malignancies and to define predictive factors of death in Korean patients with idiopathic inflammatory myopathy (IIM).

METHODS

From January 1989 to May 2011, 162 patients were diagnosed with IIM at a university hospital in Korea. The medical records were retrospectively reviewed. The clinical findings of the patients were compared for malignancy, and the prognostic factors predicting death were analyzed.

RESULTS

Malignancies were found in 17 patients (10.5 %), all of whom had a significantly lower frequency of interstitial lung disease (ILD) and an older age at onset. The main causes of death were ILD and malignancy. Older age at diagnosis, presence of malignancy, rapidly progressive ILD and minimal creatinine phosphokinase (CPK) elevation were independent risk factors for death.

CONCLUSIONS

Malignancy was one of the most serious risk factor for death in our patients with IIM. Early discovery of malignancy is important, and an extensive investigation for common malignancies in each region should be done at diagnosis and for a minimum of 2 years thereafter. As minimally elevated CPK levels in ILD patients may be associated with fatal ILD, an early evaluation and a more aggressive treatment of ILD should be considered in these patients.

Interaction of HLA-DRB1*03 and smoking for the development of anti-Jo-1 antibodies in adult idiopathic inflammatory myopathies: a European-wide case study

Objectives

HLA-DRB1*03 is strongly associated with anti-Jo-1-positive idiopathic inflammatory myopathies (IIM) and there is now increasing evidence that Jo-1 antigen is preferentially expressed in lung tissue. This study examined whether smoking was associated with the development of anti-Jo-1 antibodies in HLA-DRB1*03-positive IIM.

Methods

IIM cases were selected with concurrent information regarding HLA-DRB1 status, smoking history and anti-Jo-1 antibody status. DNA was genotyped at DRB1 using a commercial sequence-specific oligonucleotide kit. Anti-Jo-1 antibody status was established using a line blot assay or immunoprecipitation.

Results

557 Caucasian IIM patients were recruited from Hungary (181), UK (99), Sweden (94) and Czech Republic (183). Smoking frequency was increased in anti-Jo-1-positive IIM cases, and reached statistical significance in Hungarian IIM (45% Jo-1-positive vs 17% Jo-1-negative, OR 3.94, 95% CI 1.53 to 9.89, p<0.0001). A strong association between HLA-DRB1*03 and anti-Jo-1 status was observed across all four cohorts (DRB1*03 frequency: 74% Jo-1-positive vs 35% Jo-1-negative, OR 5.55, 95% CI 3.42 to 9.14, p<0.0001). The frequency of HLA-DRB1*03 was increased in smokers. The frequency of anti-Jo-1 was increased in DRB1*03-positive smokers vs DRB1*03-negative non-smokers (42% vs 8%, OR 7.75, 95% CI 4.21 to 14.28, p<0.0001) and DRB1*03-positive non-smokers (42% vs 31%, p=0.08). In DRB1*03-negative patients, anti-Jo-1 status between smokers and non-smokers was not significantly different. No significant interaction was noted between smoking and DRB1*03 status using anti-Jo-1 as the outcome measure.

Conclusion

Smoking appears to be associated with an increased risk of possession of anti-Jo-1 in HLA-DRB1*03-positive IIM cases. The authors hypothesise that an interaction between HLA-DRB1*03 and smoking may prime the development of anti-Jo-1 antibodies.

Recent advances in the immunogenetics of idiopathic inflammatory myopathy

This review summarizes the previous and current literature on the immunogenetics of idiopathic inflammatory myopathy (IIM) and updates the research progress that has been made over the past decade. A substantial part of the genetic risk for developing adult- and juvenile-onset IIM lies within the major histocompatibility complex (MHC), and a tight relationship exists between individual human leukocyte antigen alleles and specific serological subtypes, which in turn dictate clinical disease phenotypes. Multiple genetic regions outside of the MHC are increasingly being identified in conferring IIM disease susceptibility. We are still challenged with the task of studying a serologically and clinically heterogeneous disorder that is rarer by orders of magnitude than the likes of rheumatoid arthritis. An ongoing and internationally coordinated IIM genome-wide association study may provide further insights into IIM immunogenetics.

Myositis autoantibodies in Korean patients with inflammatory myositis: anti-140-kDa polypeptide antibody is primarily associated with rapidly progressive interstitial lung disease independent of clinically amyopathic dermatomyositis

Background

To investigate the association between myositis autoantibodies and clinical subsets of inflammatory myositis in Korean patients.

Methods

Immunoprecipitation was performed using the sera of classic polymyositis (PM) (n = 11) and dermatomyositis (DM) (n = 38) patients who met the Bohan and Peter criteria for definite inflammatory myositis. A panel of defined myositis autoantibodies was surveyed to investigate the association between each autoantibody and clinical subsets of inflammatory myositis.

Results

Either MSAs, anti-p140, or anti-p155/140 antibodies were found in 63.3% (31/49) of the study subjects. Anti-140-kDa-polypeptide (anti-p140) (18.4%, 9/49) and anti-155/140-kDa polypeptide (anti-p155/140) (16.3%, 8/49) antibodies were the most common, followed by anti-Mi2 (14.3%, 7/49), anti-ARS (12.2%, 6/49) and anti-SRP (2.0%, 1/49) antibodies. All MSAs and anti-p140 and anti-p155/140 antibodies were mutually exclusive. Anti-p140 (23.7%, 9/38), anti-p155/140 (21.1%, 8/38), and anti-Mi2 (18.4%, 3/38) antibodies were found exclusively in DM patients. Anti-p140 antibody was associated with rapidly progressive interstitial lung disease (ILD) (p = 0.001), with a sensitivity of 100.0% (4/4) and a specificity of 85.3% (29/34) in DM patients. Anti-p155/140 antibody was associated with cancer-associated DM (p = 0.009), with a sensitivity of 55.6% (5/9) and a specificity of 89.7% (26/29). Cancer-associated survival was significantly worse when anti-p155/140 antibody was present (19.2 ± 7.6 vs. 65.0 ± 3.5 months, p = 0.032). Finally, anti-ARS antibodies were associated with stable or slowly progressive ILD in PM and DM patients (p = 0.005).

Conclusions

Anti-p140 and anti-p155/140 antibodies were commonly found autoantibodies in Korean patients with inflammatory myositis. Despite the lack of clinically amyopathic DM patients in the study subjects, a strong association was observed between anti-p140 antibody and rapidly progressive ILD. Anti-p155/140 antibody was associated with cancer-associated myositis and poor survival.

An update on the immunogenetics of idiopathic inflammatory myopathies: major histocompatibility complex and beyond

PURPOSE OF REVIEW

To update the reader on immunogenetic advances in idiopathic inflammatory myopathy (IIM) over the past 18 months.

RECENT FINDINGS

In Caucasian IIM, despite a shared association with the human leukocyte antigen (HLA) 8.1 ancestral haplotype (HLA-DRB1*03-DQA1*05-DQB1*02), anti-Jo-1 and anti-PM-Scl antibody-positive cases have differing IIM clinical phenotypes. A study of the HLA-DPB1 region has shown that DPB1*0101 is associated with anti-Jo-1 positivity but not with anti-PM-Scl. IIM single nucleotide polymorphism studies have demonstrated associations in the protein tyrosine phosphatase, nonreceptor type 22, tumour necrosis factor alpha and interleukin-1 genes. The GM 13 allotype has been confirmed as a risk factor in Caucasian IIM. In inclusion body myositis, the HLA 8.1 ancestral haplotype may not only influence disease susceptibility but also disease expression. A follow-up study including a meta-analysis of the apolipoprotein E gene in inclusion body myositis suggests that this gene does not confer risk of disease.

SUMMARY

Although a substantial part of the genetic risk for developing adult and juvenile IIM lies within the major histocompatibility complex, recent research suggests that genetic regions outside of the major histocompatibility complex are also potentially involved in conferring IIM disease susceptibility, although with more modest effect sizes. An ongoing and internationally coordinated IIM genome-wide association scan may provide further insights into IIM immunogenetics.

HLA-DPB1 associations differ between DRB1*03 positive anti-Jo-1 and anti-PM-Scl antibody positive idiopathic inflammatory myopathy

OBJECTIVE

The HLA 8.1 ancestral haplotype (HLA-B*08/DRB1*03/DQA1*05/DQB1*02) is associated with adult/juvenile idiopathic inflammatory myopathy (IIM), but confers a greater strength of association in patients possessing anti-Jo-1 or anti-PM-Scl antibodies. The HLA-DPB1 gene is centromeric to other HLA class II loci and separated by a recombination hotspot. We investigated whether HLA-DPB1 associations differ between anti-Jo-1 and anti-PM-Scl antibody-positive IIM cases.

METHODS

Two hundred and thirty-three adult IIM patients (73% females, 49.4 +/- 13.6 years) with PM (n = 89), DM (n = 88) and myositis associated with another CTD (n = 55) and 85 juvenile DM patients (75% females, 6.2 +/- 3.6 years) were compared with 678 UK Caucasian controls. Patients/controls were genotyped for HLA-DPB1 and DRB1 alleles. Myositis-specific and associated antibodies were identified in cases using immunoprecipitation.

RESULTS

HLA-DPB1*0101 was associated with IIM overall [22 vs 13% controls, corrected probability (P(corr)) = 2 x 10(-03); odds ratio (OR) 2.0; 95% CI 1.4, 2.9], PM (P(corr) = 7 x 10(-03); OR 2.5; 95% CI 1.5, 4.4) and anti-Jo-1 (P(corr) = 3 x 10(-5); OR 4.1; 95% CI 2.1, 7.8). No significant DPB1*0101 difference was present between anti-PM-Scl cases and controls. The HLA-DPB1*0101 association in IIM overall cases was dependent on the presence of DRB1*03. A number of HLA-DRB1*03/DPB1 haplotypes were identified, but only DRB1*03/DPB1*0101 was associated with anti-Jo-1 antibody-positive cases.

CONCLUSIONS

The HLA-DRB1*03/DPB1*0101 haplotype is a risk factor for anti-Jo-1 antibody-positive IIM. Thus, although DRB1*03 is strongly associated with possession of either anti-Jo-1 or anti-PM-Scl, differing antibody associations are observed at the HLA-DPB1 locus.

Immunoglobulin gene polymorphisms are susceptibility factors in clinical and autoantibody subgroups of the idiopathic inflammatory myopathies

OBJECTIVE

To investigate possible associations of GM and KM markers with adult and juvenile forms of the idiopathic inflammatory myopathies (IIMs) in Caucasian and African American patients.

METHODS

We performed serologic analyses of polymorphic determinants associated with immunoglobulin gamma heavy chains (GM) and kappa light chains (KM) in large populations of Caucasian patients (n= 514 [297 adults and 217 children]) and African American patients (n=123 [73 adults and 50 children]) with IIM representing the major clinical and autoantibody groups.

RESULTS

For Caucasian patients with dermatomyositis (DM), the Gm 3 23 5,13 phenotype was a risk factor in both adults (odds ratio [OR] 2.2, corrected P [Pcorr]=0.020) and children (OR 2.2, Pcorr=0.0013). Of interest, the GM 13 allotype was a risk factor for juvenile DM in both Caucasian subjects (OR 3.9, Pcorr<0.0001) and African American subjects (OR 4.8, Pcorr=0.033). However, the Gm 1,3,17 5,13,21 phenotype was a risk factor for juvenile DM in Caucasian subjects but not African American subjects. Among the IIM autoantibody groups, Gm 3 23 5,13 was a risk factor in Caucasian adults with anti-Jo-1 autoantibodies (OR 3.4, Pcorr=0.0031), while the GM 3 allotype was protective in adults with anti-threonyl-transfer RNA synthetase or anti-U RNP autoantibodies (OR 0.1, Pcorr=0.047 and OR 0.2, Pcorr=0.034, respectively). In contrast, GM 6 was a risk factor in African American adults with anti-signal recognition particle autoantibodies (OR 7.5, Pcorr=0.041).

CONCLUSION

These data suggest that polymorphic alleles of GM and KM loci are differentially associated with IIM subgroups defined by age, ethnicity, clinical features, and autoantibody status, and expand the list of immune response genes that are possibly important in the pathogenesis of myositis.

HLA polymorphisms in African Americans with idiopathic inflammatory myopathy: allelic profiles distinguish patients with different clinical phenotypes and myositis autoantibodies

OBJECTIVE

To investigate possible associations of HLA polymorphisms with idiopathic inflammatory myopathy (IIM) in African Americans, and to compare this with HLA associations in European American IIM patients with IIM.

METHODS

Molecular genetic analyses of HLA-A, B, Cw, DRB1, and DQA1 polymorphisms were performed in a large population of African American patients with IIM (n = 262) in whom the major clinical and autoantibody subgroups were represented. These data were compared with similar information previously obtained from European American patients with IIM (n = 571).

RESULTS

In contrast to European American patients with IIM, African American patients with IIM, in particular those with polymyositis, had no strong disease associations with HLA alleles of the 8.1 ancestral haplotype; however, African Americans with dermatomyositis or with anti-Jo-1 autoantibodies shared the risk factor HLA-DRB1*0301 with European Americans. We detected novel HLA risk factors in African American patients with myositis overlap (DRB1*08) and in African American patients producing anti-signal recognition particle (DQA1*0102) and anti-Mi-2 autoantibodies (DRB1*0302). DRB1*0302 and the European American-, anti-Mi-2-associated risk factor DRB1*0701 were found to share a 4-amino-acid sequence motif, which was predicted by comparative homology analyses to have identical 3-dimensional orientations within the peptide-binding groove.

CONCLUSION

These data demonstrate that North American IIM patients from different ethnic groups have both shared and distinct immunogenetic susceptibility factors, depending on the clinical phenotype. These findings, obtained from the largest cohort of North American minority patients with IIM studied to date, add additional support to the hypothesis that the myositis syndromes comprise multiple, distinct disease entities, perhaps arising from divergent pathogenic mechanisms and/or different gene-environment interactions.

Atteinte pulmonaire au cours des polymyosites et des dermatomyosites

Interstitial lung disease is a serious complication of polymyositis/dermatomyositis and leads to death from chronic respiratory insufficiency in 30 to 66% of cases. It is a criterion of poor prognosis in these disorders. Its onset occurs at variable points in the course of polymyositis/dermatomyositis, and precedes them in half of all cases. Presentation may also vary: acute (25%), insidious (60%), or infraclinical, discovered fortuitously (15%). The examinations of choice for early screening are high-resolution computed tomography (CT) and pulmonary function tests, which should be performed during the initial work-up and during ongoing surveillance. Moreover, high-resolution CT also makes it possible to determine the type of histologic lesions in the interstitial lung disease. Today, diagnosis of this disease does not generally require histological confirmation; nonspecific interstitial lung disease seems to be the most common histologic form of lung damage in polymyositis/dermatomyositis (40 to 80%). Anti-Jo1 antibodies are a sensitive marker of interstitial lung disease during polymyositis/dermatomyositis, and close surveillance of lung function is recommended in patients with these autoantibodies. Systematic testing for them is also justified in patients with apparently idiopathic interstitial lung disease, to rule out underlying polymyositis/dermatomyositis. No clear treatment protocols have been established for interstitial lung disease during polymyositis/dermatomyositis. Corticosteroid treatment is the first choice. Its combination with cyclophosphamide may be most effective in corticosteroid-resistant forms of polymyositis/dermatomyositis, especially when begun early; it may also be appropriate to begin corticosteroids as soon as factors predicting poor prognosis are detected.

Immunogenetic risk and protective factors for the idiopathic inflammatory myopathies: distinct HLA-A, -B, -Cw, -DRB1, and -DQA1 allelic profiles distinguish European American patients with different myositis autoantibodies

The idiopathic inflammatory myopathies (IIM) are systemic connective tissue diseases defined by chronic muscle inflammation and weakness associated with autoimmunity. We have performed low to high resolution molecular typing to assess the genetic variability of major histocompatibility complex loci (HLA-A, -B, -Cw, -DRB1, and -DQA1) in a large population of European American patients with IIM (n = 571) representing the major myositis autoantibody groups. We established that alleles of the 8.1 ancestral haplotype (8.1 AH) are important risk factors for the development of IIM in patients producing anti-synthetase/anti-Jo-1, -La, -PM/Scl, and -Ro autoantibodies. Moreover, a random forests classification analysis suggested that 8.1 AH-associated alleles B*0801 and DRB1*0301 are the principal HLA risk markers. In addition, we have identified several novel HLA susceptibility factors associated distinctively with particular myositis-specific (MSA) and myositis-associated autoantibody (MAA) groups of the IIM. IIM patients with anti-PL-7 (anti-threonyl-tRNA synthetase) autoantibodies have a unique HLA Class I risk allele, Cw*0304 (pcorr = 0.046), and lack the 8.1 AH markers associated with other anti-synthetase autoantibodies (for example, anti-Jo-1 and anti-PL-12). In addition, HLA-B*5001 and DQA1*0104 are novel potential risk factors among anti-signal recognition particle autoantibody-positive IIM patients (pcorr = 0.024 and p = 0.010, respectively). Among those patients with MAA, HLA DRB1*11 and DQA1*06 alleles were identified as risk factors for myositis patients with anti-Ku (pcorr = 0.041) and anti-La (pcorr = 0.023) autoantibodies, respectively. Amino acid sequence analysis of the HLA DRB1 third hypervariable region identified a consensus motif, 70D (hydrophilic)/71R (basic)/74A (hydrophobic), conferring protection among patients producing anti-synthetase/anti-Jo-1 and -PM/Scl autoantibodies. Together, these data demonstrate that HLA signatures, comprising both risk and protective alleles or motifs, distinguish IIM patients with different myositis autoantibodies and may have diagnostic and pathogenic implications. Variations in associated polymorphisms for these immune response genes may reflect divergent pathogenic mechanisms and/or responses to unique environmental triggers in different groups of subjects resulting in the heterogeneous syndromes of the IIM.

A novel autoantibody to a 155-kd protein is associated with dermatomyositis

OBJECTIVE

In polymyositis and dermatomyositis (DM), identified autoantibodies occur in <50% of adult patients and in a smaller proportion of children. This study was undertaken as part of a larger effort to define novel autoantibodies that assist in the clinical evaluation of myositis.

METHODS

Sera from children and adults satisfying criteria for idiopathic inflammatory myopathies and from patients with other connective tissue diseases (CTDs), patients with noninflammatory myopathies, and healthy individuals were tested for autoantibodies by immunoprecipitation (IP). A previously unrecognized autoantibody that immunoprecipitated a 155-kd protein along with a weaker 140-kd protein was seen. When the presence of this anti-p155 autoantibody in test sera was suggested based on IP results, it was confirmed by immunoblotting of immunoprecipitates.

RESULTS

Sera from 51 of 244 myositis patients (21%), including 30 with juvenile DM (29%), 5 with juvenile CTD-associated myositis (33%), 8 with adult DM (21%), 6 with cancer-associated DM (75%), and 2 with adult CTD-associated myositis (15%), were found to have anti-p155 autoantibody. One of 49 patients with lupus, and none of 89 others without myositis, had anti-p155. Caucasian patients with anti-p155 had a unique HLA risk factor, DQA1*0301 (odds ratio 5.4, corrected P = 0.004). In adults with anti-p155, of several clinical features assessed only the frequency of V-sign rash was increased, but patients with this antibody were clinically distinct from those with autoantibodies to aminoacyl-transfer RNA synthetases.

CONCLUSION

A newly recognized autoantibody, anti-p155, is associated with DM and cancer-associated DM, and is one of the most common autoantibodies in this condition, occurring as frequently in children as in adults. The clinical features and immunogenetics associated with anti-p155 differ from those associated with antisynthetases.

Immunogenetic risk and protective factors for the idiopathic inflammatory myopathies: distinct HLA-A, -B, -Cw, -DRB1 and -DQA1 allelic profiles and motifs define clinicopathologic groups in caucasians

The idiopathic inflammatory myopathies (IIM) are systemic connective tissue diseases in which autoimmune pathology is suspected to promote chronic muscle inflammation and weakness. We have performed low to high resolution genotyping to characterize the allelic profiles of HLA-A, -B, -Cw, -DRB1, and -DQA1 loci in a large population of North American Caucasian patients with IIM representing the major clinicopathologic groups (n = 571). We confirmed that alleles of the 8.1 ancestral haplotype were important risk markers for the development of IIM, and a random forests classification analysis suggested that within this haplotype, HLA-B*0801, DRB1*0301 and/ or closely linked genes are the principal HLA risk factors. In addition, we identified several novel HLA factors associated distinctly with 1 or more clinicopathologic groups of IIM. The DQA1*0201 allele and associated peptide-binding motif (KLPLFHRL) were exclusive protective factors for the CD8+ T cell-mediated IIM forms of polymyositis (PM) and inclusion body myositis (IBM) (pc < 0.005). In contrast, HLA-A*68 alleles were significant risk factors for dermatomyositis (DM) (pc = 0.0021), a distinct clinical group thought to involve a humorally mediated immunopathology. While the DQA1*0301 allele was detected as a possible risk factor for IIM, PM, and DM patients (p < 0.05), DQA1*03 alleles were protective factors for IBM (pc = 0.0002). Myositis associated with malignancies was the most distinctive group of IIM wherein HLA Class I alleles were the only identifiable susceptibility factors and a shared HLA-Cw peptide-binding motif (AGSHTLQWM) conferred significant risk (pc = 0.019). Together, these data suggest that HLA susceptibility markers distinguish different myositis phenotypes with divergent pathogenetic mechanisms. These variations in associated HLA polymorphisms may reflect responses to unique environmental triggers resulting in the tissue pathospecificity and distinct clinicopathologic syndromes of the IIM.

Have recent immunogenetic investigations increased our understanding of disease mechanisms in the idiopathic inflammatory myopathies?

PURPOSE OF REVIEW

The idiopathic inflammatory myopathies (IIM) continue to provide a challenge given the variable effectiveness of the available treatments, and immunogenetic studies are ongoing to further elucidate IIM disease mechanisms. This review examines how recent research has improved our understanding of the mechanisms that lead to IIM.

RECENT FINDINGS

HLA-DRB1 studies in a large homogenous cohort of UK Caucasian patients have confirmed that polymyositis (PM) and dermatomyositis (DM) are not genetically identical diseases while other studies have shown that tumor necrosis factor alpha is genetically implicated in disease susceptibility. Some remarkable results from an international collaboration, correlating gene-environment interactions, clearly suggest that ultraviolet light is capable of modulating both clinical and immunologic features of IIMs. Studies on microchimerism are unraveling interesting associations in juvenile DM patients, and bolstering the hypothesis that myositis may be an 'allo-immune' disease. mRNA gene expression profiling is helping to increase our understanding of myositis pathogenesis, whilst animal models have provided new information on the roles of Th1 responses and nitric oxide synthase in muscle disease. New candidate genes have been examined in inclusion body myositis (IBM), and a novel gene transfer experiment has been conducted, which led to significant changes in expression of the IBM phenotype.

SUMMARY

Improving the understanding of the immunogenetics and immunopathogenesis of the IIMs may in the future provide novel therapeutic targets, and thus improve outcomes in these difficult diseases.

Myositis: an update on pathogenesis

PURPOSE OF REVIEW

The etiology and much about the pathogenesis of the inflammatory myopathies remain a mystery. In this review, we investigate recent research efforts to understand the pathogenesis of the diverse entities of polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM), diseases that result from interactions between environmental risk factors and genetic susceptibility.

RECENT FINDINGS

Over the past year, there has been considerable progress toward better understanding of IBM, with relatively few developments toward understanding PM and DM. Although these diseases may share some common clinical phenotypic and serologic components, they differ on a molecular and cellular level.

SUMMARY

The need for definitive, safer therapies in these diseases makes vital the search for defining detailed pathogenesis of inflammation and muscle fiber damage at the molecular level.

Foreign cells in polymyositis: Could stem cell transplantation and pregnancy-derived chimerism lead to the same disease?

A growing number of hematopoietic stem cell transplantation centers have reported that patients with chronic graft versus host disease (GVHD) can develop polymyositis (PM). GVHD-PM is similar to idiopathic PM in signs, symptoms, laboratory values, electromyography, radiography, and histology, suggesting that the two conditions may share a similar mechanism in pathogenesis. In chronic GVHD-PM, interactions between allogeneic donor cells and host cells lead to chronic inflammation. In idiopathic PM, the foreign cells could be partially human leukocyte antigen-matched maternal or fetal cells acquired during pregnancy. Thus, PM can be added to the list of potentially allo-autoimmune diseases in which pregnancy-derived microchimerism may play a role.

Idiopathic inflammatory myopathies - myositis

The inflammatory myopathies - myositis - encompass a heterogeneous group of chronic muscle disorders of unknown origin and with varying prognoses. New clinical phenotypes of myositis have been identified since the most widely used classification criteria were proposed in 1975. Based on clinical and histopathological features, inclusion body myositis was identified. Furthermore, the myositis-specific autoantibodies may also identify different clinical phenotypes and serve as prognostic markers. The different classifications and inclusion criteria that have been used in different studies make some epidemiological data uncertain. In order to improve our knowledge of causative factors, as well as of pathogenic mechanisms, there is a need for revision and also for an international acceptance of the classification criteria. During recent years, our knowledge has increased regarding the role of some genetic and environmental factors that could affect susceptibility for developing myositis as well as the prognosis. Whether there is an association between myositis and malignancies has been a subject of controversy for many years and recent epidemiological data have brought some clarification on this issue.

Genetic and environmental risk factors for idiopathic inflammatory myopathies

Although the studies discussed are beginning to reveal a number of genetic and possible environmental risk factors for myositis, further investigations are needed to fully understand and classify these syndromes. The difficulties in this process include small numbers of subjects with varying disease phenotypes available for study, polygenic risk factors for which it remains unclear which are primary and which are secondary or linked genes, and the lack of validated environmental exposure assessment tools. New technologies and international collaborative approaches, however, may overcome some of these difficulties and allow us to identify genetic and environmental risk factors, as well as the critical gene-environment interactions in the IIM and its subgroups. Nonetheless, our understanding of these diseases is still in the early stages. Although we have learned a great deal about these disorders through detailed investigations over the last several decades, we have even further to go to understand the environmental triggers and genetic susceptibilities for the myositis syndromes.

Juvenile dermatomyositis: immunogenetics, pathophysiology, and disease expression

Data are rapidly accumulating documenting disease susceptibility may be linked to genetic markers (DQA1*0501 or related alleles) which are associated with upregulation of IFN-alpha/beta inducible genes elicited in response to an antigen which may be viral. Continued immune-mediated inflammation, resulting in partial lipodystrophy and pathological calcifications, may be fanned by the increased production of TNF alpha usually associated with the TNF alpha-308A allele.

Differences in idiopathic inflammatory myopathy phenotypes and genotypes between Mesoamerican Mestizos and North American Caucasians: ethnogeographic influences in the genetics and clinical expression of myositis

OBJECTIVE

As part of a larger, worldwide study of the ethnogeography of myositis, we evaluated the clinical, serologic, and immunogenetic features of Mestizo (Mexican and Guatemalan) and North American Caucasian patients with idiopathic inflammatory myopathy (IIM).

METHODS

Clinical manifestations, autoantibodies, HLA-DRB1 and DQA1 alleles, and immunoglobulin Gm/Km allotypes were compared between 138 Mestizos with IIM and 287 Caucasians with IIM, using the same classification criteria and standardized questionnaires.

RESULTS

IIM in Mestizo patients was characterized by a higher proportion of dermatomyositis (69% of adult Mestizos versus 35% of adult Caucasians; P < 0.001) and anti-Mi-2 autoantibodies (30% versus 7% of adults, respectively, and 32% versus 4% of children, respectively; P < 0.01). Genetic risk factors also differed in these populations. Whereas Mestizos had no HLA risk factors for IIM, HLA-DRB1*0301, the linked allele DQA1*0501, and DRB1 alleles sharing the first hypervariable region motif (9)EYSTS(13) were major risk factors in Caucasian patients with IIM. Furthermore, different HLA-DRB1 and DQA1 alleles were associated with anti-Mi-2 autoantibodies (DRB1*04 and DQA1*03 in Mestizos and DRB1*07 and DQA1*02 in Caucasians). Immunoglobulin gamma-chain allotypes Gm(1), Gm(17) (odds ratio for both 11.3, P = 0.008), and Gm(21) (odds ratio 7.3, P = 0.005) and kappa-chain allotype Km(3) (odds ratio 7.3, P = 0.005) were risk factors for IIM in Mestizos; however, no Gm or Km allotypes were risk or protective factors in Caucasians. In addition, Gm and Km phenotypes were unique risk factors (Gm 1,3,17 5,13,21 and Gm 1,17 23 21 and Km 3,3) or protective factors (Km 1,1) for the development of myositis and anti-Mi-2 autoantibodies (Gm 1,2,3,17 23 5,13,21) in adult Mestizos.

CONCLUSION

IIM in Mesoamerican Mestizos differs from IIM in North American Caucasians in the frequency of phenotypic features and in the immune-response genes predisposing to and protecting from myositis and anti-Mi-2 autoantibodies at 4 chromosomal loci. These and other data suggest the likelihood that the expression of IIM is modulated by different genes and environmental exposures around the world.

HLA class II haplotypes associated with pulmonary interstitial lesions of polymyositis/dermatomyositis in Japanese patients

To elucidate the immunogenetic background of idiopathic inflammatory myopathies (IIM) such as polymyositis (PM), dermatomyositis (DM) and any overlapping subsets, with other collagen vascular diseases, HLA class I antigens and class II alleles were determined and compared from individuals with various clinical and serological features of IIM, including pulmonary interstitial lesions (PI). Seventy-three Japanese patients with myositis (32 PM, 18 DM, 23 overlapped subsets) and 62 healthy unrelated controls were enrolled onto the study. Statistical differences between groups were determined by the Fisher's exact probability test. Serum fluorescent antinuclear antibody, rheumatoid factor (RF), anti-SS-A/Ro antibody, anti-Jo1 antibody and anti-U1 RNP antibody were examined using routine methods. PI was detected by chest X-ray and/or computed tomography. In patients with DM, the frequency of the HLA-DRB1*1302-DQA1*0102-DQB1*0604 haplotype was significantly higher than in the healthy controls (42.1% vs 17.7%), and in the patients with PM (42.1% vs 9.4%). Furthermore, the frequency of the HLA-DRB1*0405-DQA1*03-DQB1*0401 haplotype was higher in the PM patients with PI than in the controls (50.0% vs 17.7%), and PM without PI (50.0% vs 5.5%). These results suggest that in terms of HLA class II association, Japanese DM and PM, and PM with and without PI, belong to different clinical groups.

[Interstitial lung diseases in polymyositis and dermatomyositis]

PURPOSE

Interstitial lung disease is one of the most common respiratory manifestations in polymyositis and dermatomyositis. It still remains a severe complication of the disease, leading to death related to ventilatory insufficiency in 30-66% of patients.

CURRENT KNOWLEDGE AND KEY POINTS

Time onset of interstitial lung disease is variable, although interstitial lung disease onset precedes initial manifestations of polymyositis/dermatomyositis in roughly half of the patients. Moreover, clinical presentation of interstitial lung disease can be dichotomized, according to patients' pulmonary manifestations, into: 1) both acute and aggressive lung disease similar to Hamman-Rich syndrome; 2) slowly progressive lung disease; and 3) an asymptomatic pattern. The methods of choice adopted for early diagnosis of interstitial lung disease are high-resolution computed tomography scan and pulmonary function tests, which should be performed during both initial evaluation of polymyositis/dermatomyositis and follow-up. Because anti-JO1 antibody is considered to be a marker of interstitial lung disease in polymyositis/dermatomyositis, close pulmonary follow-up of anti-JO1-positive patients with polymyositis is therefore required for early detection of subclinical impairment. Furthermore, histological lung findings provide prognostic data; patients with bronchiolitis obliterans organizing pneumonia (BOOP) indeed appear to have a more favorable outcome than those with usual interstitial pneumonia or diffuse alveolar damage. Finally, as a guide to both the severity and progress of interstitial lung disease, the significance of other investigations, notably bronchoalveolar lavage, remains controversial.

FUTURE PROSPECTS AND PROJECTS

Specific therapy of interstitial lung disease has not yet been clearly established in polymyositis/dermatomyositis patients. Corticosteroid therapy is considered the first line of therapy for polymyositis/dermatomyositis patients with interstitial lung disease. The association of cyclophosphamide and corticosteroids may be the most effective in patients with steroid-resistant interstitial lung disease. Early diagnosis and management of this disease is therefore of the utmost importance.

Juvenile dermatomyositis: the association of the TNF alpha-308A allele and disease chronicity

Little is known concerning factors associated with the outcome of juvenile dermatomyositis (JDM), which can be variable and lethal. Previous work has documented that the association of DQA1*0501 with JDM is higher than in control groups and that the first symptoms (rash and weakness) of JDM appear to follow evidence of an infectious process--most frequently upper respiratory in nature. Preliminary data show that a long period of symptoms being left untreated before starting therapy and the TNF alpha-308A allele are associated with prolonged JDM symptoms requiring > or = 36 months of immunosuppressive therapy. A short duration of untreated disease is associated with a relative increase in CD8(+) T cells and CD56(+) natural killer (NK) cells in the untreated JDM muscle biopsy compared with a longer duration of untreated disease. The TNF alpha-308A allele is overrepresented in white children with JDM. In addition, it is associated with pathologic calcifications, increased production of TNF alpha by peripheral blood mononuclear cells in vitro and JDM muscle fibers in vivo, and occlusion of capillaries, which may be mediated in part by elevated circulating levels of thrombospondin-1, a potent anti-angiogenic factor. We speculate that DQA1*0501 is associated with JDM susceptibility to an infectious process, eliciting and activating NK cells early in the disease course. We conclude that the TNF alpha-308A allele indicates directly (or is a surrogate marker of) children with JDM who produce higher concentrations of TNF alpha in response to this undefined inflammatory stimulus, as well as increased concentrations of TSP-1 with resultant small vessel occlusion, contributing to subsequent disease chronicity.

Update on the genetics of the idiopathic inflammatory myopathies

A number of lines of investigation suggest that, as is likely the case for other autoimmune diseases, the idiopathic inflammatory myopathies (IIM) develop as a result of specific environmental exposures in genetically susceptible individuals. Current data imply that multiple genes are involved in the etiology of these complex disorders. Targeted gene studies and whole genome approaches have begun to identify several genetic risk factors for autoimmune diseases, but the rarity and heterogeneity of the IIM have limited our knowledge of their associated genes. Current findings suggest that human leukocyte antigen (HLA) genes on chromosome 6, particularly HLA DRB1*0301 and the linked allele DQA1*0501, have the strongest associations with all clinical forms of IIM in white patients. Different HLA alleles, however, may confer risk or protection for myositis in distinct ethnic, serologic, and environmental exposure groups. Non-HLA genetic risk factors, which have been documented for other autoimmune diseases, are now being identified for the IIM. These include polymorphic genes encoding immunoglobulin heavy chains (defined by serologic markers known as Gm allotypes), cytokines and their receptors, and certain proteins that accumulate in the myocyte vacuoles of inclusion body myositis patients. Selected allelic polymorphisms of interleukin-1 receptor antagonist variable number tandem repeats and genes for tumor necrosis factor alpha and interleukin-1 alpha also have recently been associated with IIM. The pathogenic bases for the differences among the many clinically, pathologically and immunologically defined syndromes known as the IIM will be elucidated through a better understanding of the multiple genes that define risks for their development, as well as through investigations of gene-gene and gene-environment interactions.

Polymorphisms in the IL-1 receptor antagonist gene VNTR are possible risk factors for juvenile idiopathic inflammatory myopathies

Although HLA-DRB1 and -DQA1 alleles have been associated with adult and juvenile idiopathic inflammatory myopathies (JIIM), they only partially account for the genetic risk for these autoimmune disorders. Because IL-1alpha and IL-1beta, and the anti-inflammatory competitive inhibitor, IL-1 receptor antagonist (IL-1Ra), have been implicated in the pathogenesis of myositis, we assessed the role of variable number tandem repeat (VNTR) polymorphisms of the IL-1Ra gene (IL-1RN) in the aetiology of JIIM: IL-1RN VNTR polymorphisms were performed on 250 JIIM patients and 471 race-matched controls and were correlated with clinical characteristics. The IL-1RN A1 allele, associated with increased proinflammatory activity, was found to be a risk factor for Caucasians with JIIM (96.0% carriage rate versus 90.2% in race-matched controls, Pcorr = 0.037, odds ratio (OR) = 2.5, confidence interval (CI) = 1.1-5.8), but not for African-Americans, in whom the A3 allele was a possible risk factor (7.0% versus 1.1% in race-matched controls, Pcorr = 0.07, OR = 6.5, CI = 1.1-40.3). IL-1RN genotypes did not correlate with circulating levels of IL-1Ra, which were higher in patients than in controls. The polymorphic IL-1RN locus could be the first non-MHC genetic risk factor identified for JIIM, and different alleles may confer susceptibility for different ethnic groups.

Familial autoimmunity and the idiopathic inflammatory myopathies

Many lines of evidence suggest that autoimmune diseases result from chronic immune activation following environmental exposures in genetically susceptible individuals. A genetic basis for autoimmunity is supported by twin and family studies, candidate gene investigations, animal models, and whole genome microsatellite scans. These findings predict, and clinical observations support, familial clustering of a number of individual autoimmune diseases, notably lupus, multiple sclerosis, type-1 diabetes mellitus, rheumatoid arthritis, and recently the idiopathic inflammatory myopathies. Yet, not only is the same autoimmune disease increased in prevalence in pedigrees of persons affected with a given disorder, but other autoimmune diseases are as well. We review these data and propose a hypothesis consistent with these findings. This model posits that a rheumatic disease, as currently classified, is actually composed of a number of elemental disorders. Each of these is defined by the minimal necessary and sufficient environmental exposures and genes that result in a pathology leading to a given sign-symptom complex.

Idiopathic inflammatory muscle disease: clinical aspects

Although much remains to be learned about the immune-mediated myositis syndromes, information generated from recent studies in a number of areas may assist physicians in patient management. Topics reviewed here include: data supporting the association of myositis with cancer and the appropriate evaluations for malignancy in a myositis patient; an approach to the assessment of patients with dermatomyositis sine myositis; the usefulness of the clinicopathological and serological classifications; a discussion of whether childhood and adult myositis are the same or different entities; a review of those prognostic factors to consider in the clinical management of myositis patients; current approaches and their limitations for assessing disease activity and damage. To improve our limited understanding of the myositis syndromes, national and international collaborations are needed to obtain the necessary numbers of subjects, given the rarity and heterogeneity of these disorders.