Trends in idiopathic inflammatory myopathies: cross-sectional data from the German National Database

Rheumatology International - To describe trends in outcomes among patients with idiopathic inflammatory myopathies (IIM) over two decades. From 1997 to 2017, a total of 1079 IIM patients were...     

Cardiac involvement in idiopathic inflammatory myopathies detected by cardiac magnetic resonance imaging

Clinical Rheumatology - Cardiac involvement in idiopathic inflammatory myopathies (IIM) adversely affects prognosis but is commonly sub-clinical. Cardiac magnetic resonance imaging (CMR) is an...     

Pathogenesis of the idiopathic inflammatory myopathies

The inflammatory myopathies, commonly described as idiopathic, are a group of acquired diseases characterized by an inflammatory infiltrate of the skeletal muscle. On the basis of clinical and immuno-pathological features, three major diseases can be identified: dermatomiositis (DM), polymyositis (PM) and inclusion body myositis (IBM). Immunopathogenesis mechanisms are crucial for discriminating between the three different subsets of inflammatory myopathies. DM is a complement-mediated microangiopathy affecting skin and muscle. PM and IBM are T cell-mediated disorders, where CD8-positive cytotoxic T cells invade muscle fibres expressing MHC class I antigens. This article summarizes the main immunopathological markers. The impact of this new knowledge must be defined in relation to potential therapeutic targets for idiopathic inflammatory myopathies.     

Pathogenesis of idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies, myositis, are characterized by a chronic course with decreased muscle endurance and by infiltrates of T lymphocytes and macrophages in muscle tissue. Treatment with immunosuppressives rarely leads to recovery of muscle function, despite abolishment of inflammatory cell infiltrates in muscle tissue. Therefore, other mechanisms than immunemediated muscle fiber damage are likely to contribute to the pathogenesis. One such non-immune-mediated muscle dysfunction could be caused by a disturbed microcirculation due to capillary loss or to phenotypically changed endothelial cells in the capillaries. These aberrations may affect the micro-environment of muscle tissue and lead to local tissue hypoxia with development of a secondary metabolic myopathy. Another possible non-immune-mediated mechanism leading to muscle dysfunction is the newly identified endoplasmatic reticulum (ER) stress response in myositis. The ER stress response is thought to be a consequence of the up-regulation of major histocompatibility complex class I in muscle fibers. These newly identified molecular pathways could play a major role in the pathogenesis of myositis and could be important targets in the development of new therapies.     

Pathogenesis of idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies, myositis, are characterized by a chronic course with decreased muscle endurance and by infiltrates of T lymphocytes and macrophages in muscle tissue. Treatment with immunosuppressives rarely leads to recovery of muscle function, despite abolishment of inflammatory cell infiltrates in muscle tissue. Therefore, other mechanisms than immune-mediated muscle fiber damage are likely to contribute to the pathogenesis. One such non-immune-mediated muscle dysfunction could be caused by a disturbed microcirculation due to capillary loss or to phenotypically changed endothelial cells in the capillaries. These aberrations may affect the micro-environment of muscle tissue and lead to local tissue hypoxia with development of a secondary metabolic myopathy. Another possible non-immune-mediated mechanism leading to muscle dysfunction is the newly identified endoplasmatic reticulum (ER) stress response in myositis. The ER stress response is thought to be a consequence of the up-regulation of major histocompatibility complex class I in muscle fibers. These newly identified molecular pathways could play a major role in the pathogenesis of myositis and could be important targets in the development of new therapies.     

Muscle pathological features and extra-muscle involvement in idiopathic inflammatory myopathies with anti-mitochondrial antibody

ObjectiveAnti-mitochondrial antibodies (AMAs) can be detected in some idiopathic inflammatory myopathy (IIM) patients. We aimed to investigate the clinical features of IIM patients with AMAs.MethodsWe retrospectively analysed 1,167 consecutive patients with IIM for AMA-associated myositis and compared them to age- and gender-matched AMA-negative IIM patients.ResultsTwenty-nine patients (2.5%) were identified with AMA-positive myositis; eight of them had primary biliary cholangitis (PBC). There were no significant differences in skin rash, dysphagia, interstitial lung disease, and muscle strength between AMA-positive patients and AMA-negative patients. Of 23 cases, 12 (52.2%) showed immune-mediated necrotizing myopathy (IMNM)-like pathological features. amongst AMA-positive patients, 11 of 16 patients with isolated anti-AMAs were classified as IMNM which was significantly higher than that of patients with coexistent anti-AMAs and myositis-specific antibodies (p = 0.026). Moreover, subclinical cardiac involvement was significantly more common in AMA-positive patients than in AMA-negative patients (21/29 VS 33/116, p<0.001). In addition, patients without PBC had a significantly higher incidence of abnormal echocardiography findings than that of patients with PBC (p = 0.009). Patients without heart abnormalities took significantly less time to achieve disease remission and prednisone tapering to <10 mg than patients with heart abnormalities (p = 0.000 and p = 0.001, respectively).ConclusionsIMNM was a major histopathological finding in IIM patients with isolated AMAs. AMAs were significantly associated with subclinical cardiac involvement in IIM. PBC seemed to be a protective factor for abnormal echocardiography findings in AMA-positive patients. Patients without heart involvement took less time to achieve disease remission and prednisone tapering off.     

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 hypthesis 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.     

Clinical presentation of the idiopathic inflammatory myopathies

The hallmark of the inflammatory myopathies is muscle weakness. Although this feature can lead to significant disability and impairment of activities of daily living, its initial presentation may not be recognized early. Older individuals, in particular, may feel that the changes caused by myositis reflect the effects of aging rather than those of a disease process, and diagnosis, therefore, may be delayed. This factor has negative impact on the response to therapy. Inclusion body myositis, with its insidious onset in older people, and laboratory findings which may not be markedly abnormal, presents a diagnostic challenge. DM, with its characteristic symptomatic rash, is generally brought to medical attention more quickly. Another area of diagnostic concern occurs when associated organ involvement precedes myopathy. This has been observed, for example, with interstitial lung disease, and again represents a challenge to physicians. In this connection, the antisynthetase syndrome presenting with fevers, Raynaud's features, arthritis, or pulmonary involvement may not initially be recognized as a manifestation of inflammatory muscle disease. Each subgroup of IIM may present with a variety of extramuscular features that can complicate diagnosis and alter therapy and prognosis. This is particularly true for the pulmonary, GI, and cardiac manifestations and when cancer is associated with myositis. For these reasons, such features of IIM should be carefully evaluated, treated, and monitored over the course of the illness; in some cases these may play a greater role in determining the outcome of patients with IIM than the muscle involvement itself. It is hoped that in the future increased familiarity with the manifestations of the inflammatory myopathies, together with a better understanding of the underlying pathogenesis, will lead to more rapid diagnosis and more effective treatments.     

Differential diagnosis of idiopathic inflammatory myopathies

Symmetric proximal muscle weakness has many potential etiologies. An onset over weeks to months and elevated serum levels of muscle enzymes point to the diagnosis of an idiopathic inflammatory myopathy, including dermatomyositis, polymyositis, and inclusion body myositis. However, there is a broad differential diagnosis, including certain muscular dystrophies, metabolic myopathies, drug- or toxin-induced myotoxicity, neuropathies, and infectious myositides. The differentiation is critical for defining appropriate treatment. In addition, an alternative diagnosis may explain the lack of response to immunosuppressive treatment for some patients with polymyositis. Careful clinical evaluation and choice of available diagnostic tests are required to establish the correct diagnosis.     

Physical activity and disablement in the idiopathic inflammatory myopathies

PURPOSE OF REVIEW: The sequelae associated with idiopathic inflammatory myopathy (IIM) often result in disability and decreased quality of life. Our understanding of how exercise mitigates disability may be facilitated through the use of a conceptual model. This review describes the enablement-disablement model applied to myositis and explores the role of physical activity in the enablement process. RECENT FINDINGS: National and international organizations have revised their disablement models by acknowledging disability as a relational concept, refining the relationship of disability to quality of life, and incorporating the role of intervention through the enablement process. Disability associated with IIM may be complicated by aging-related comorbidities and decreased physical activity. However, data indicate that both short-term and long-term aerobic training results in improved aerobic capacity and decreased disability in adults with IIM. Strengthening regimens have also resulted in decreased functional limitations and disability for adults with polymyositis and dermatomyositis. While comprehensive exercise programs have not been shown to exacerbate disease activity or damage in people with IIM, their effectiveness for individuals with inclusion body myositis (IBM) remains uncertain. SUMMARY: Physical activity constitutes a valuable enablement strategy that can reduce disability in adults with IIM. Use of the disablement-enablement model and ICF taxonomy in conjunction with outcomes across disablement domains may augment further investigation of the effectiveness of exercise interventions. Additional research is needed to better understand the relationship between disease severity and optimal exercise dosage, the effects of long-term exercise in children with IIM, and the physiologic response to exercise in people with IBM.     

Magnetic resonance imaging in the idiopathic inflammatory myopathies.

We examined the usefulness of magnetic resonance imaging (MRI) in detecting active muscle disease in 40 patients with idiopathic inflammatory myopathies (IIM). Ten patients without evidence of an inflammatory neuromuscular disease were also studied. The fat-suppressive (STIR) image signal intensity correlated with clinical disease activity and, in most cases, with the presence of inflammation on muscle biopsy. Increased STIR signal intensity paralleled disease activity in 3 patients followed serially. MRI provided a detailed anatomic view of the extent of muscle changes in these diseases. Because of inherent limitations of other measures of disease in these disorders, MRI may prove to be a useful complimentary test for assessing disease activity and guiding therapeutic decisions and biopsy in the idiopathic inflammatory myopathies.     

Oral cyclophosphamide in treatment of patients with refractory idiopathic inflammatory myopathies: a retrospective observational study

To describe the use of oral cyclophosphamide (PO CYC) in a single center longitudinal cohort of patients with idiopathic inflammatory myopathies (IIM). Patients using PO CYC were identified through a retrospective chart review of a myositis cohort at a single academic center. PO CYC dose, duration, adverse events, and disease activity measures before and after CYC were analyzed. Disease activity measures included muscle enzymes, manual muscle testing (MMT8), 100-mm visual analog scale (VAS), and 1–4 Likert scale for physician global assessment. Fourteen patients were treated with PO CYC within the cohort between 2008 and 2017; 9 dermatomyositis (DM), 3 polymyositis (PM), and 2 with immune-mediated necrotizing myopathy (IMNM). Age was 51.1 (40–72) years and the cumulative dose of PO CYC was 41 (2–131) grams over duration of 12.4 (0.5–43) months, mean (range) for all. All patients had severe refractory IIM, 10 (72%) with ILD, 3 (21%) with cardiac involvement and 4 (29%) were dependent in most activities of daily living. Median number of prior failed therapies was 4.5 (range 3–6) including intravenous CYC in 5 patients. Disease activity measures significantly improved following CYC use and concomitant daily prednisone dose decreased. The most common adverse events during CYC therapy were infections. We report the first cohort study of PO CYC use in IIM patients with severe, treatment refractory disease. Further trials are needed to verify these results as well as to evaluate long-term safety outcomes.     

Characterization of relapses in adult idiopathic inflammatory myopathies

The objective of the current report was to determine the relapse rates and characterize the nature of relapses during the disease course of adult patients with idiopathic inflammatory myopathies (IIM). A retrospective cohort study of 53 medical records of patients with polymyositis (PM), dermatomyositis (DM), connective tissue disease (CTD)-associated myositis, and malignancy-associated myositis at an academic rheumatology center was performed. Medical records were reviewed to determine clinical presentation, initial treatment, and clinical follow-up, with an emphasis on relapses. Relapses were defined as a sustained elevation in serum creatine kinase (CK) levels in the absence of an alternative etiology. Patients were followed for an average of 65±43 months. All patients received corticosteroids, and 35 patients received additional immunosuppressive medications as part of their initial treatment. Serum CK levels normalized in 51 patients, and muscle strength normalized in 43 patients. Biochemical relapse was observed in 33 patients (65%). Patients with PM and CTD-associated myositis had a higher relapse rate compared to DM and malignancy-associated myositis patients. Multiple relapses were observed in 17 patients. Relapses tended to occur within the first 2 years after treatment initiation and during the tapering phase of treatment. No risk factors were unequivocally identified, although advanced age and increased duration of symptoms prior to treatment initiation had nonsignificant associations with increased risk of relapse. In conclusion, initial treatment of IIM results in a high rate of normalization of serum CK and muscle weakness. However, physicians should be aware of the high rate of relapse in patients with IIM.