Idiopathic inflammatory myopathies: diagnostic criteria, classification and epidemiological features

Novel B-cell subsets as potential biomarkers in idiopathic inflammatory myopathies: insights into disease pathogenesis and disease activity

Idiopathic inflammatory myopathies are a heterogeneous group of rare autoimmune disorders characterized by progressive muscle weakness and the histopathologic findings of inflammatory infiltrates in muscle tissue. Although their pathogenesis remains indefinite, the association of autoantibodies with clinical manifestations and the evidence of high effectiveness of depleting therapies suggest that B cells could be implicated. Therefore, we explored the landscape of peripheral B cells in this disease by multiparametric flow cytometry, finding significant numerical decreases in memory and double-negative subsets, as well as an expansion of the naive compartment relative to healthy controls, that contribute to defining disease-associated B-cell subset signatures and correlating with different clinical features of patients. Additionally, we determined the potential value of these subsets as diagnostic biomarkers, thus positioning B cells as neglected key elements possibly participating in idiopathic inflammatory myopathy onset or development.

Sarcoplasmic Myxovirus Resistance Protein A: A Study of Expression in Idiopathic Inflammatory Myopathy

Background

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune diseases affecting primarily proximal muscles. Major subtypes include dermatomyositis, polymyositis, inclusion body myositis, immune-mediated necrotizing myopathy and antisynthetase syndrome. Overexpression of sarcoplasmic myxovirus-resistance protein A (MxA) has been observed in muscle biopsy specimens of dermatomyositis but is rarely seen in other subtypes of IIM and other myopathies.

Objective

We evaluate the expression of sarcoplasmic MxA and its diagnostic value in IIM and other myopathies.

Methods

One hundred and thirty-eight muscle biopsy specimens with the diagnosis of IIM and other myopathies from 2011 to 2020 were reviewed and stained for MxA by immunohistochemistry. The difference of the expression of MxA between IIM and other myopathies was analyzed by Fisher's exact test, and the sensitivity and specificity of MxA immunohistochemistry in the diagnosis of IIM were assessed.

Results

MxA protein was positive in 16/138 (11.6%) specimens. All 12 dermatomyositis specimens positive for MxA protein were positive in perifascicular area pattern. Only dermatomyositis specimens had a significantly higher percentage of positive sarcoplasmic MxA expression than specimens of other subtypes of IIM (p<0.001). Sarcoplasmic MxA expression for dermatomyositis diagnosis had a sensitivity of 46.15% (95% CI 26.59-66.63%) and a specificity of 94.44% (95% CI 81.34-99.32%) with the positive and negative likelihood ratio of 8.31 (95% CI 2.03-34.01) and 0.57 (95% CI 0.40-0.82), respectively.

Conclusion

The MxA immunohistochemistry is highly specific for dermatomyositis and should be added to a routine inflammatory panel of muscle biopsy. MxA expression should be cautiously interpreted to avoid pitfalls.

Incidence and prevalence, and medication use among adults living with dermatomyositis: an Alberta, Canada population-based cohort study

Dermatomyositis is a rare disease characterized by progressive muscle weakness and skin rashes. Estimates of incidence and prevalence are fundamental measures in epidemiology, but few studies have been conducted on dermatomyositis. To address this knowledge gap, we conducted a population-based study to determine the contemporary incidence (between 2013 and 2019) and prevalence (2019) of adults living with dermatomyositis using administrative health data in Alberta, Canada. We also described disease-related medication use, as there are very few approved medications for the treatment of dermatomyositis, and no Canadian therapeutic guidelines. The average age- and sex-standardized annual incidence of dermatomyositis was 2.8-3.0 cases per 100,000 adults, and prevalence was 28.6 cases per 100,000 adults, which is greater than reported in other cohorts. Dermatomyositis-related medication use decreased from 73% in the first year to 46% in the eighth year after diagnosis. Glucocorticoids were the most commonly used drug class, often taken concurrently with various immunomodulatory agents; this medication use aligns with empirically-based recommendations and the few therapeutic guidelines for dermatomyositis. Considering that Alberta may have one of the highest rates of dermatomyositis among adults, further research on the burden of disease is warranted for planning within the health care system.

A Narrative Review of Acthar Gel for the Treatment of Myositis

Idiopathic inflammatory myopathies (IIMs) are autoimmune disorders characterized by symmetric proximal muscle weakness and chronic inflammation, with an increased risk of morbidity and mortality. The current standard of care includes traditional immunosuppressive pharmacotherapies; however, some patients cannot tolerate or do not adequately respond to these therapies, highlighting the need for alternative treatments for refractory disease. Acthar^® Gel (repository corticotropin injection) is a naturally sourced mixture of adrenocorticotropic hormone analogs and other pituitary peptides that has been approved by the US Food and Drug Administration since 1952 for use in patients with two subgroups of IIMs, dermatomyositis (DM) and polymyositis (PM). However, it has not been routinely used in the treatment of IIMs. While Acthar may induce steroidogenesis, it also has a steroid-independent mechanism of action by exerting immunomodulatory effects through the activation of melanocortin receptors on immune cells, such as macrophages, B cells, and T cells. Recent clinical trials, retrospective analyses, and case reports add to the growing evidence suggesting that Acthar may be effective in patients with DM and PM. Here we review the current evidence supporting the safety and efficacy of Acthar for the treatment of refractory DM and PM.

Work situation, work ability and expectation of returning to work in patients with systemic autoimmune myopathies

OBJECTIVES

To document the work situation, the work ability and the expectation of returning to work among adult patients with systemic autoimmune myopathies (SAMs), and to identify the factors associated with each of these outcomes.

METHODS

Cross-sectional study. The work situation (performing paid work vs out of work) was ascertained via a structured questionnaire. For those who were working, we applied the Work Ability Index (WAI; scale 7-49); and for those who were out of work, we applied the Return-to-Work Self-Efficacy questionnaire (RTW-SE; scale 11-66).

RESULTS

Of the 75 patients with SAMs included, 33 (44%) were doing paid work and 42 (56%) were out of work. The work situation was independently associated with physical function, assessed by the Health Assessment Questionnaire-Disability Index (HAQ-DI). A 1-point increase in the HAQ-DI (scale 0-3) decreased the chance of doing paid work by 66% (95% CI: 0.16, 0.74; P = 0.007). Patients performing paid work had a mean WAI of 33.5 (6.9). The following variables were associated with a decrease in the WAI score in the regression model: female sex (-5.04), diabetes (-5.94), fibromyalgia (-6.40), fatigue (-4.51) and severe anxiety (-4.59). Among those out of work, the mean RTW-SE was 42.8 (12.4). Cutaneous manifestations and >12 years of education were associated with an average increase of 10.57 and 10.9 points, respectively, in the RTW-SE. A 1-point increase in the HAQ-DI decreased the RTW-SE by 4.69 points.

CONCLUSION

Our findings highlight the poor work participation in a well-characterized sample of working-age patients with SAMs. Strategies to improve work-related outcomes in these patients are urgently needed.

Impaired muscle strength is associated with ultrastructure damage in myositis

The muscle fiber ultrastructure in Idiopathic Inflammatory Myopathies (IIM) has been scarcely explored, especially in Inclusion Body Myositis. The aim of this study was to implement the Scanning Electron Microscopy (SEM) in a small cohort of IIM patients, together with the characterization of immunological profile for a better understanding of the pathophysiology. For immunological profile characterization, we identified the presence of autoantibodies (Ro-52, OJ, EJ, PL7, PL12, SRP, Jo-1, PMScl75, PMScl100, Ku, SAE1, NXP2, MDA5, TIF1γ, Mi-2α, Mi-2β) and quantified cytokines (IL-1β, IFN-α2, IFN-γ, TNF-α, IL-6, IL-10, IL-12p70, IL-17A, IL-18, IL-23, IL-33) and chemokines (CCL2, CXCL8). The histological analysis was made by hematoxylin-eosin staining while the muscle fiber ultrastructure was characterized by SEM. We observed changes in the morphology and structure of the muscle fiber according to muscle strength and muscle enzymes. We were able to find and describe muscle fiber ultrastructure with marked irregularities, porosities, disruption in the linearity and integrity of the fascicle, more evident in patients with increased serum levels of muscle enzymes and diminished muscle strength. Despite the scarce reports about the use of SEM as a tool in all clinical phenotypes of IIM, our work provides an excellent opportunity to discuss and reframe the clinical usefulness of SEM in the diagnostic approach of IIM.

Advances in the management of idiopathic pulmonary fibrosis and progressive pulmonary fibrosis

Similarly to idiopathic pulmonary fibrosis (IPF), other interstitial lung diseases can develop progressive pulmonary fibrosis (PPF) characterized by declining lung function, a poor response to immunomodulatory therapies, and early mortality. The pathophysiology of disordered lung repair involves common downstream pathways that lead to pulmonary fibrosis in both IPF and PPF. The antifibrotic drugs, such as nintedanib, are indicated for the treatment of IPF and PPF, and new therapies are being evaluated in clinical trials. Clinical, radiographic, and molecular biomarkers are needed to identify patients with PPF and subgroups of patients likely to respond to specific therapies. This article reviews the evidence supporting the use of specific therapies in patients with IPF and PPF, discusses agents being considered in clinical trials, and considers potential biomarkers based on disease pathogenesis that might be used to provide a personalized approach to care.

Systematic review of physical exercise for patients with idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM) are systemic autoimmune connective tissue diseases. The safety and effectiveness of exercise for patients with idiopathic inflammatory myopathies remains unclear. This study aimed to systematically review the evidence for physical exercise among patients with idiopathic inflammatory myopathies. Relevant experimental studies were identified through searching the PubMed, Cochrane, Embase, Scopus, and CINAHL databases, and studies involving any type of physical exercise for ≥1 month were considered. The primary outcome was muscle strength, and the secondary outcomes included aerobic fitness, functional performance, health status, quality of life, activities of daily living, pain, and fatigue. Eight randomized controlled trials and thirteen nonrandomized uncontrolled trials were reviewed. Physical exercise appeared safe, with several positive effects. However, selection or allocation biases and small sample sizes affected the certainty of the evidence. While physical exercise appeared safe for patients with idiopathic inflammatory myopathies with several positive effects, studies of a higher methodological quality and involving patients with active disease are needed. Furthermore, to design optimal exercise programs, consistent and sensitive outcome measures are needed to facilitate comparisons of results from different studies.

Outcomes of Pregnancy in Women With Inflammatory Myositis: A Cohort Study From India

OBJECTIVES

Idiopathic inflammatory myositis (IIM) commonly affects women in the childbearing age group. Both disease activity and immunosuppressants used may have adverse effects on fertility and outcomes of pregnancy. We explored these outcomes in a cohort of women with IIM.

METHODS

Women 18 years or older with IIM (Bohan and Peter criteria) were interviewed for demography, menstrual status, history of conception, outcomes, and disease features. Comparisons were drawn between pregnancies occurring before and after onset of disease.

RESULTS

Eighty-one IIM patients with median age of 32 years (interquartile range, 26-50 years) and disease duration of 4 years (interquartile range, 2-9 years) were interviewed. Forty-five patients had dermatomyositis, 20 had polymyositis, and 16 had overlap myositis. Sixty-three patients had conceived before disease onset, resulting in 205 pregnancies and 155 live births over 315.2 patient-years of follow-up.After disease onset, there were 24 pregnancies (6 live births, 16 spontaneous abortions, and 2 induced abortions) in 7 women over 77.5 patient-years. Of the live births, 1 had cleft palate, 1 had low birth weight, and 1 was preterm. None of the patients who conceived had antiphospholipid antibodies.Obstetric complications (relative risk [RR] = 7.6; p < 0.0001) and fetal complications (RR = 2.7; p = 0.002) occurred more frequently in pregnancies after the onset of myositis, although there was no difference in maternal complications. Conception after the onset of myositis had higher risk of abortion (RR = 3.6; p < 0.0001).

CONCLUSIONS

Women with IIM suffer from poor fetal outcomes as well as high rates of spontaneous abortion rates in the absence of clinical or serologic anti-phospholipid syndrome.

Muscle type from which satellite cells are derived plays a role in their damage response

The aim of this study was to evaluate the response of satellite cells to muscular atrophies which possess different pathological characteristics and which were induced by distinct damages. Right lower limbs of rats were exposed to denervation or disuse and later its tibialis anterior (TA) or soleus (SOL) muscles were analyzed. After confirming their functional impairments indicated by common but distinct pathological and electrophysiological characteristics, the quantitative polymerase chain reaction analysis of Pax7 and Pax3 expressions and the number of Pax7^+ve and Pax3^+ve cells were analyzed sequentially at day 0, day 7, and day 14. TA muscles of both denervation- and disuse-induced atrophy models showed persisted low level of Pax7 expression from day 7 (0.91 ± 0.23 and 0.31 ± 0.07, P = 0.06, n = 6) through day 14 (1.09 ± 0.15 and 0.4 ± 0.09 [P < 0.05]). On the other hand, significant elevations were observed in Pax3 expression in both atrophy models (2.73 ± 0.46 and 2.75 ± 0.26 [P < 0.05]) at day 7. Similar to TA muscle, resembled pattern of Pax7 and Pax3 expression changes were observed between the SOL muscles of denervation- and disused-atrophy models. These trends were further confirmed by the changes in Pax7^+ve and Pax3^+ve cell numbers of TA and SOL muscles in both atrophy models. Despite the distinct pathological findings, similar patterns in the changes of Pax3 and Pax7 expressions and the changes of Pax7^+ve and Pax3^+ve cell numbers were observed between the denervation- and disuse-induced atrophy models and this commonality was admitted among the muscle type. Therefore, we claim that the muscle regeneration orchestrated by satellite cells was governed by the muscle type in which satellite cells reside.

Safety of fertility treatments in women with systemic autoimmune diseases (SADs)

Introduction: Systemic Autoimmune Diseases (SADs) include systemic lupus erythematosus, antiphospholipid antibody syndrome, rheumatoid arthritis, systemic sclerosis, Sjogren's syndrome, mixed connective tissue disease, idiopathic inflammatory myopathies and vasculitis. SADs often occur in women of childbearing age and can affect fertility. Both infertility treatments and fertility preservation techniques are thus often indicated. Areas covered: The literature regarding the safety of fertility-related drugs for both fertility preservation and infertility treatment in patients affected by SADs was reviewed. Based on current knowledge, all the options for fertility preservation should be contemplated in patients with SADs who are at risk for fertility loss, including GnRH analogue administration, oocyte/embryo vitrification and ovarian tissue cryopreservation. Similarly, if pregnancy is not contraindicated in a patient with a SAD, neither should be any fertility treatment. Expert opinion: Women with SADs should postpone conception until a stable disease has been achieved for at least 6 months. When infertility treatments are needed, women with antiphospholipid antibodies should receive concomitant anticoagulation. If in vitro fertilization/intra-cytoplasmic sperm injection and embryo transfer is required, ovarian hyperstimulation and the inherent risk of thrombosis should be eliminated by GnRH-agonist trigger and cycle segmentation. Counselling about adherence to anti-rheumatic therapy to prevent disease exacerbations is also critical.

Case of Anti-Single Recognition Particle-Mediated Necrotizing Myopathy After Influenza Vaccination

Immune-mediated necrotizing myopathy is a very rare inflammatory disease affecting skeletal muscles. Immune-mediated necrotizing myopathy may be associated with myositis-specific autoantibodies including anti-single recognition particle and anti-3-hydroxy-3- methylglutaryl-coenzyme A reductase, infectious agents (HIV or hepatitis C), other connective tissue disorders (such as scleroderma), and malignancy. We reported a 28-year-old healthy woman presented with subacute onset ascending muscle weakness 2 weeks after an annual influenza vaccination. Cerebral Spinal Fluid study showed normal cell counts with elevated protein and nerve conduction study showed reduced diffuse compound muscle action potential amplitudes suggesting a diagnosis of Guillain-Barré syndrome. Despite treatment using intravenous immunoglobulin, her condition continued to get worse with new bulbar and respiratory muscle weakness. Eventually, the diagnosis of anti-single recognition particle-mediated necrotizing myopathy was made based on elevated creatine kinase, thigh magnetic resonance imaging, muscle biopsy, and positive antibody testing. Our patient responded to the combination of intravenous immunoglobulin, prednisone, and anti-CD20 monoclonal antibody, rituximab.

Effect of butylphthalide intervention on experimental autoimmune myositis in guinea pigs

Idiopathic inflammatory myopathies are a group of rare muscular diseases that are characterized by acute, subacute or chronic proximal and symmetric muscle weakness, muscle fiber necrosis and infiltration of inflammatory cells, particularly activated CD8⁺ cytotoxic T cells and phagocytes. 3-n-butylphthalide (NBP) protects mitochondria and reduces the inflammatory response in multiple disease models. In myositis, it has remained elusive whether NBP can protect muscle cells from muscle fiber injury. Experimental autoimmune myositis (EAM) was induced in a total of 40 guinea pigs by myosin immunization. After 4 weeks, low- or high-dose NBP solution was intraperitoneally injected. Saline solution was used as a negative control. After 10 days, the clinical manifestations were assessed by determining rodent grasping power, histopathological changes, Ca²⁺-adenosinetriphosphatase (ATPase) activity by an ATPase kit, and mRNA expression of interferon (IFN)-γ, retinoic acid receptor-related orphan nuclear receptor (ROR)γt and forkhead box (Fox) p3 in muscle tissue by reverse-transcription quantitative polymerase chain reaction analysis. It was demonstrated that NBP improved the myodynamia of guinea pigs with EAM and reduced the pathological inflammatory cell infiltration in a dose-dependent manner. NBP improved the Ca²⁺-ATPase activity of the muscle mitochondrial membrane and muscle plasma membrane in animals with EAM. It also reduced the mRNA expression of IFN-γ and RORγt, and significantly increased the mRNA expression of Foxp3 in muscle tissue. These results provided a basis for the consideration of NBP as a novel agent for the treatment of myositis and other muscular diseases associated with autoimmunity and inflammation.

Mortality in idiopathic inflammatory myopathy: results from a Swedish nationwide population-based cohort study

Patients with idiopathic inflammatory myopathies (IIMs) suffer an increased burden of comorbidities, but data on mortality in recently diagnosed IIM are conflicting. Also, little is known when, if ever, in relation to IIM diagnosis, mortality is increased.

Methods

A population-based IIM cohort of patients diagnosed between 2002 and 2011 and general population comparators were identified using healthcare registers. They were linked to the cause of death register for follow-up.

Results

224 (31%) of the 716 patients with IIM and 870 (12%) of the 7100 general population died during follow-up. This corresponded to a mortality rate of 60/1000 person-years in IIM and 20/1000 person-years in the general population. The cumulative mortality at 1 year after diagnosis was 9% in IIM and 1% in the general population, and increased in both IIM and the general population with time. The overall hazard ratio (HR) 95%CI of death comparing IIM with the general population was 3.7 (3.2 to 4.4). When we stratified on time since diagnosis, we noted an increase in mortality already within the first year of diagnosis compared with the general population, HR 9.6 (95% CI 6.9 to 13.5). This HR then plateaued around 2 after >10 years with the disease, although the estimates were not statistically significant. Malignancies, diseases of the circulatory and respiratory system were common causes of death.

Conclusion

Mortality is increased in patients with contemporary IIM. The increased mortality was noted within a year of diagnosis, which calls for extra vigilance during the first year of IIM diagnosis.

The epidemiology of dermatomyositis in northwestern Thrace region in Turkey: epidemiology of dermatomyositis in Turkey

Dermatomyositis (DM) is a rare disease that may affect the skeletal muscles and the skin. Literature data on its incidence and prevalence are limited. There are no data on its incidence or prevalence in Turkey. Patients diagnosed with DM at the Trakya University Medical Faculty, Department of Rheumatology from November 2004 to November 2014 were reviewed retrospectively. Patients' clinical and demographic features, laboratory data, treatment modalities, follow-up durations, disease courses, outcomes, and complications were evaluated. Our study included 23 patients with DM; 14 were females and 9 were males (female/male: 1.55). Over the course of the study, the annual incidence of DM was 3.7 per million (95% CI 0-18.8) person years, and the overall prevalence was 32.2 per million (95% CI 18.1-46.3). Incidence in women was higher (4.6/1,000,000 person years) compared to men (2.9/1,000,000 person years). The frequencies of most common findings were as follows: heliotrope rash (82.6%), Gottron papules (87%), proximal myopathy (78.3%), and facial erythema (60.9%). In our hospital-based study, the frequency of DM was lower than those reported in North America; however, they were similar to European countries.

Dermatomyositis Induced by Hepatitis B Virus-related Hepatocellular Carcinoma: A Case Report and Review of the Literature

Dermatomyositis or polymyositis as a paraneoplastic syndrome of hepatocellular carcinoma (HCC) is an uncommon event. Few cases have been reported in the literature. We herein report the case of a 55-year-old man with chronic hepatitis B and alcoholism who presented with skin rash. Abdominal computed tomography revealed multiple hypervascular liver tumors consistent with HCC. He subsequently developed dysphagia with proximal limb weakness. Laboratory tests and electromyography demonstrated inflammatory myopathy. We therefore diagnosed the patient with HCC-induced dermatomyositis. Prednisolone and anti-viral therapy were administered; however, the patient died two months later due to the progression of the disease. We review the cases of HCC-induced dermatomyositis and polymyositis in the literature.

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.

Strain sonoelastography of inflammatory myopathies: comparison with clinical examination, magnetic resonance imaging and pathologic findings

OBJECTIVE

To evaluate strain sonoelastography (SSE) in patients with inflammatory myopathies (IM) compared with clinical examination, MRI and pathologic findings.

METHODS

18 lesions from 17 consecutive patients with IM (5 males and 12 females; mean age, 41.2 years; range, 11-67 years) were assessed with SSE after MRI. The ratio of strain in the target muscle (A) and a nearby normal muscle (B), defined as the strain index value (SR) (B/A), was calculated automatically. Elastograms were assigned an elasticity score according to the degree and distribution of strain induced by manual compression. Ultrasonography and MRI were analyzed in conjunction with clinical information, biochemical data, final clinical diagnosis and grading of pathology. Correlations between SR and qualitative analyses of MRI and ultrasonography, elasticity score, biochemical data and final clinical diagnosis were analyzed using Pearson's correlation coefficient.

RESULTS

The SR of the target muscles was high in patients with IM (mean 3.14; range, 0.95-5.93 ± 1.42). The correlations between SR and pathologic grading and elasticity score were statistically significant (p < 0.05). There was no significant agreement between SR and other clinical and radiologic parameters.

CONCLUSION

Muscle hardness, as semi-quantitatively measured by SSE, was increased in cases of IM. The correlation between the SR and the pathologic grading suggests that SSE could be an important tool in not only the diagnosis of but also in measuring the degree of muscular inflammation.

ADVANCES IN KNOWLEDGE

This work describes a correlation between tissue elasticity and pathology in IM.

Cost-utility analysis of intravenous immunoglobulin for the treatment of steroid-refractory dermatomyositis in Thailand

INTRODUCTION

Intravenous immunoglobulin (IVIG) has been shown to be effective in treating steroid-refractory dermatomyositis (DM). There remains no evidence of its cost-effectiveness in Thailand.

OBJECTIVE

Our objective was to estimate the cost utility of IVIG as a second-line therapy in steroid-refractory DM in Thailand.

METHODS

A Markov model was developed to estimate the relevant costs and health benefits for IVIG plus corticosteroids in comparison with immunosuppressant plus corticosteroids in steroid-refractory DM from a societal perspective over a patient's lifetime. The effectiveness and utility parameters were obtained from clinical literature, meta-analyses, medical record reviews, and patient interviews, whereas cost data were obtained from an electronic hospital database and patient interviews. Costs are presented in $US, year 2012 values. All future costs and outcomes were discounted at a rate of 3% per annum. One-way and probabilistic sensitivity analyses were also performed.

RESULTS

Over a lifetime horizon, the model estimated treatment under IVIG plus corticosteroids to be cost saving compared with immunosuppressant plus corticosteroids, where the saving of costs and incremental quality-adjusted life-years (QALYs) were $US4738.92 and 1.96 QALYs, respectively. Sensitivity analyses revealed that probability of response of immunosuppressant plus corticosteroids was the most influential parameter on incremental QALYs and costs. At a societal willingness-to-pay threshold in Thailand of $US5148 per QALY gained, the probability of IVIG being cost effective was 97.6%.

CONCLUSIONS

The use of IVIG plus corticosteroids is cost saving compared with treatment with immunosuppressant plus corticosteroids in Thai patients with steroid-refractory DM. Policy makers should consider using our findings in their decision-making process for adding IVIG to corticosteroids as the second-line therapy for steroid-refractory DM patients.

Statin-associated Autoimmune Myopathies: A Pathophysiologic Spectrum

Background

Statins have recently been reported to cause a rare autoimmune inflammatory and/or necrotic myopathy that begins or persists after drug cessation.

Methods

We report on 26 patients seen at a neuromuscular centre between 2005 and 2011 who demonstrated muscle weakness/myalgias and creatine kinase elevations during or after statin treatment with continuation of signs and symptoms despite statin withdrawal.

Results

All patients were treated with immunosuppressive therapy with good response; all improved biochemically and 86% improved clinically. Sixty-five percent of patients who attempted to taper off immunosuppressive therapy relapsed. We report on a novel finding whereby five of the seven patients who underwent multiple biopsies throughout their disease demonstrated a transformation of their histological diagnosis, with four progressing from having myofibre necrosis with minimal or no inflammation to a diagnosis of polymyositis.

Conclusions

This study offers preliminary evidence that statin-associated necrotizing myopathy and statin-associated polymyositis may not be separate entities but are part of the same pathophysiological spectrum. Both entities respond well to immunosuppression.

The diagnosis and classification of polymyositis

Polymyositis is classified as a separate entity among idiopathic inflammatory myopathies but it is considered as the least common since it is an exclusion diagnosis. This myopathy usually presents with subacute-chronic symmetric proximal limb weakness, although some extramuscular manifestations are common. Creatine kinase values may be increased up to 50-fold in active disease. Muscle biopsy is characterized by endomysial inflammatory infiltrate consisting predominantly of CD8+ T cells that invade healthy muscle fibres expressing the MHC-I antigen. Although serum autoantibodies, EMG and imaging techniques can help in diagnosis, muscle histopathology is a pivotal value. The clinical picture together with the pathological findings confers the also called PM pattern. A broad differential diagnosis is needed before concluding a diagnosis of pure PM. Sporadic inclusion-body myositis, toxic, endocrine and metabolic myopathies as well as muscular dystrophies are the major categories to be ruled out. Finally, a diagnostic algorithm for suspected cases of PM is also proposed.

Prevalence and incidence of polymyositis and dermatomyositis in Japan

OBJECTIVES

To estimate the number of patients with polymyositis/dermatomyositis (PM/DM) in Japan and the prevalence rate and incidence rate of the disease.

METHODS

The electronic database in the nationwide registration system on intractable diseases from 2003 to 2010 was utilized to identify the number of prevalent and incident cases of PM/DM. The electronic data entry rate was used to establish the total number of registered cases.

RESULTS

The estimated total number of patients with PM/DM and the prevalence rate in Japan in 2010 were 17,000 and 13.2 per 100,000 population, respectively. The prevalence of PM/DM ranged from 10 to 13 per 100,000 population with a trend toward increasing over time. The incidence of PM/DM was estimated within the range 10-13 per 1,000,000 person-years, except for 2003.

CONCLUSIONS

We report the prevalence and incidence of PM/DM recently in Japan for the first time at the nationwide population level. Because the prevalence seems to be increasing recently, continued monitoring of these epidemiologic features is required.

Acquired myopathy/dystrophies

Diseases of muscle may be congenital or acquired. They cause muscle weakness without sensory loss. The onset, distribution, and clinical course help to differentiate the type of muscle disorder. The diagnostic workup may include laboratory examination, electrodiagnostic studies, and muscle biopsy. A definitive diagnosis leads to better decision making with regard to treatment, genetic education, prognosis, functional expectations, and the impact of exercise on muscle function.

Diagnosis and treatment of the idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIMs) are rare disorders with the unifying feature of proximal muscle weakness. These diseases include polymyositis(PM), dermatomyositis (DM) and inclusion body myositis (IBM) as the most common. The diagnosis is based on the finding of weakness on exam, elevated muscles enzymes, characteristic histopathology of muscle biopsies, electromyography abnormalities and rash in DM. Myositis-specific antibodies have been helpful in defining subsets of patients with different responses to treatment and prognosis. The cornerstone of therapy is corticosteroids with the addition of other immunosuppressives in severe or refractory disease or patients with intolerable side effects. IBM is particularly difficult to treat but is more slowly progressive as compared with PM or DM. There is still a great need to find more effective and less-toxic therapies.

Immunological tolerance to muscle autoantigens involves peripheral deletion of autoreactive CD8+ T cells

Muscle potentially represents the most abundant source of autoantigens of the body and can be targeted by a variety of severe autoimmune diseases. Yet, the mechanisms of immunological tolerance toward muscle autoantigens remain mostly unknown. We investigated this issue in transgenic SM-Ova mice that express an ovalbumin (Ova) neo-autoantigen specifically in skeletal muscle. We previously reported that antigen specific CD4⁺ T cell are immunologically ignorant to endogenous Ova in this model but can be stimulated upon immunization. In contrast, Ova-specific CD8⁺ T cells were suspected to be either unresponsive to Ova challenge or functionally defective. We now extend our investigations on the mechanisms governing CD8⁺ tolerance in SM-Ova mice. We show herein that Ova-specific CD8⁺ T cells are not detected upon challenge with strongly immunogenic Ova vaccines even after depletion of regulatory T cells. Ova-specific CD8⁺ T cells from OT-I mice adoptively transferred to SM-Ova mice started to proliferate in vivo, acquired CD69 and PD-1 but subsequently down-regulated Bcl-2 and disappeared from the periphery, suggesting a mechanism of peripheral deletion. Peripheral deletion of endogenous Ova-specific cells was formally demonstrated in chimeric SM-Ova mice engrafted with bone marrow cells containing T cell precursors from OT-I TCR-transgenic mice. Thus, the present findings demonstrate that immunological tolerance to muscle autoantigens involves peripheral deletion of autoreactive CD8⁺ T cells.

Clinical features, pathogenesis and treatment of juvenile and adult dermatomyositis

Juvenile and adult dermatomyositis (DM) have multiple commonalities, yet display differing prevalence of features, outcomes and comorbidities. In general, compared with the disease in adults, children with DM have more vasculopathy and a greater likelihood of calcinosis, periungual and gingival telangiectasias, and ulceration, but have a better long-term prognosis with improved survival. Adults with DM are more likely to have myositis-specific antibodies, develop interstitial lung disease, have amyopathic disease, and have a marked association with malignancy and other comorbidities. Both diseases have similar features on muscle biopsy and interferon gene signature, although subtle differences can exist in pathogenesis and pathology, such as more capillary loss and a greater degree of C5b-9 complement deposition in affected muscle of juvenile patients. Initiatives are underway to improve classification, markers of disease activity and ability to predict outcome of juvenile and adult DM. The purpose of this Review is to compare and contrast the unique features between juvenile and adult disease and to outline new initiatives in the field.

Mass spectrometric determination of IgG subclass-specific glycosylation profiles in siblings discordant for myositis syndromes

Many autoimmune conditions are believed to result from chronic inflammation as a consequence of the interaction of genetic and environmental factors in susceptible individuals. One common feature in some autoimmune diseases is the decrease in terminal galactosylation of the constant region N-glycan of the total plasma immunoglobulin. To determine whether a similar pattern is characteristic for the autoimmune disorder myositis, we analyzed the antibody subclass specific glycosylation in patients with myositis, their asymptomatic siblings, and healthy unrelated age- and sex-matched controls. The antibody subclass specific glycosylation was determined from the LC-MS analyses of the IgG glycopeptides generated by trypsin digestion of the antibody heavy chain. The glycosylation profiles of the IgG subclasses were determined relative to the total abundance of all glycoforms. We found elevated amounts of glycoforms lacking terminal galactose in myositis patients. Pairwise statistical analyses reveals that galactosylation is statistically different between the myositis patients and control groups. Furthermore, the trend analysis for glycosylation indicates a pattern of decreasing galactosylation in the order controls ≥ siblings ≥ myositis patients, suggesting the existence of a genetic, immune-related predisposition in the group of asymptomatic siblings that can be detected before the onset of clinical symptoms at the level of plasma proteins.

Observations on the classification of the inflammatory myopathies

This brief review considers historical approaches to the classification of the inflammatory myopathies. The last 25 years have seen advances in our knowledge of the underlying immune mechanism but the initial trigger for the idiopathic inflammatory myopathies remains unknown. Existing classifications have their limitations, but with the absence of a "gold standard" a definitive classification is not yet possible. Despite these problems, a working classification is possible that is valuable for everyday clinical practice.