Idiopathic inflammatory myopathy (IIM) is a rare group of autoimmune diseases, characterized by chronic muscle weakness, muscle fatigue and infiltration of single nuclear cells in skeletal muscle. Its subtypes include dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM) and immune-mediated necrotizing myositis (IMNM), and the most common subtypes are DM and PM. PM is an autoimmune disease mainly manifested by muscle damage. When the skin is involved, it is called DM. The incidence of IIM was relatively low, which was 1.16-19 per million people/year, but the mortality was high and the prognosis was poor. The pathogenesis of IIM is still unclear. Previous studies suggest that both immune and non-immune mechanisms are involved in its pathogenesis, especially cellular and humoral immunity. In recent years, researchers have conducted a number of studies on the pathogenesis of IIM, especially in the study of DM/PM with the application of high-throughput biometrics. Epigenetics is a discipline that refers to the genetic phenomena of DNA methylation spectrum, chromatin structure state and gene expression spectrum transferred between cells without any changes in DNA sequence, including DNA methylation, chromatin modification and non-coding RNA changes. A large number of studies have shown that epigenetic modification plays an important role in many diseases, especially in cancer. Recent studies have also found a series of epigenetic markers related to the occurrence and development of DM/PM, mainly in the aspect of non-coding RNA changes, such as miR-10a, miR-206, etc. And there has also been some research on DNA methylation. However, no studies have been reported on whether chromatin modification is involved in the pathogenesis of DM/PM. The pathogenesis of DM/PM is complex and diverse. With the development of research, certain microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) may become biological markers for the early diagnosis of DM/PM. Therefore, this paper mainly expounds the research progress of the biomarkers of DM/PM from the aspect of epigenetics.
Biomarkers ; Dermatomyositis ; Humans ; MicroRNAs ; Muscle, Skeletal ; Polymyositis

BACKGROUND: This study aimed to estimate the incidence and prevalence of idiopathic inflammatory myopathies (IIM) and associated comorbidities in Korea from 2006 to 2015. METHODS: IIM between 2004 to 2015 were identified using the Korean National Health Insurance Service medical claim database. The case definition required more than one visit based on diagnostic codes including juvenile dermatomyositis (JDM), dermatomyositis (DM), or polymyositis (PM) and registration in the Individual Copayment Beneficiaries Program (ICBP) for rare and intractable diseases. IIM patients with a disease-free period of 24 months before the index date were defined as incident cases. The Elixhauser comorbidity score was calculated. RESULTS: Using the base case definition, 1,150 prevalent patients with IIM (117 JDM, 521 DM, 512 PM) were recorded in 2006 and 2,210 (130 JDM, 1,101 DM, 869 PM) in 2015. The prevalence was estimated at 2.3–4.0 (0.9–1.2 for JDM, 1.2–2.7 for DM, 1.4–2.1 for PM)/100,000 person-year (PY). We identified 218 incident cases of IIM in 2006 (18 JDM, 98 DM, 102 PM) and 191 cases (7 JDM, 83 DM, 101 PM) in 2015. The incidence was estimated at 2.9–5.2 (0.7–1.9 for JDM, 1.8–4.0 for DM, 1.6–3.0 for PM)/1,000,000 PY. The mean age (± standard deviation) of prevalent patients with IIM was 51.2 (± 16.9) years, and the percentage of women was 72.1%. More than two-thirds of patients (70.7%) had more than two comorbidities. Twenty percent of patients had interstitial lung diseases. CONCLUSION: In Korea, the incidence and prevalence of IIM were 2.9–5.2/1,000,000 PY and 2.3–4.0/100,000 PY, respectively.
Comorbidity ; Dermatomyositis ; Female ; Humans ; Incidence ; Korea ; Lung Diseases, Interstitial ; Myositis ; National Health Programs ; Polymyositis ; Prevalence

Dermatomyositis (DM) and polymyositis (PM) are representative idiopathic inflammatory myopathies characterized by symmetric and progressive proximal muscle weakness. Especially, DM is identified by characteristic skin lesions and has many extramuscular manifestations including various cardiac abnormalities, interstitial lung disease, and malignancy. However, involvement of peripheral nervous system in DM/PM is very rare and less known. The term “Neuromyositis” was introduced by Senator in 1893 to describe the concomitant involvement of the peripheral nervous system in DM/PM. Since then, a very few cases of neuromyositis have been reported mainly in the United States and Europe. Therefore, the pathogenetic mechanism and disease progression are unclear. In recent years, a few more cases were reported in Asia, specifically, China and Japan; however, none in Korea. Here, we describe a case of DM-associated neuromyositis in a 42-year-old man in Korea and review previous publications through literature research.
Adult ; Asia ; China ; Dermatomyositis ; Disease Progression ; Electromyography ; Europe ; Humans ; Japan ; Korea ; Lung Diseases, Interstitial ; Muscle Weakness ; Myositis ; Neural Conduction ; Peripheral Nervous System ; Peripheral Nervous System Diseases ; Polymyositis ; Skin ; United States

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune muscle diseases with systemic involvement. Patients with IIM present with varying degrees of muscle disease, cutaneous manifestations, and internal organ involvement. The diagnosis and classification of IIM is based primarily on the classification system composed of clinical features, laboratory value and muscle biopsy. In addition, the identification and characterization of myositis-related autoantibodies can help diagnosis and classification. Recently, many studies have also demonstrated that the physician can define the clinical syndromes, establish treatment strategy and predict outcomes based on the patients' myositis-specific autoantibodies (MSA) and myositis-associated antibodies (MAA) profiles. MSAs are found exclusively in IIMs and facilitate the identification of subsets of patients with relatively homogeneous clinical features. MAAs are frequently found in association with other MSA; however, they may also be detected in various connective diseases.
Antibodies ; Antibodies, Antinuclear ; Autoantibodies ; Biopsy ; Classification ; Dermatomyositis ; Diagnosis ; Humans ; Myositis ; Polymyositis

Dermatomyositis ; classification ; Humans ; Myositis ; classification ; Polymyositis ; classification

Initial discovery on sphingosine 1-phosphate (S1P) as an intracellular second messenger was faced unexpectedly with roles of S1P as a first messenger, which subsequently resulted in cloning of its G protein-coupled receptors, S1P₁₋₅. The molecular identification of S1P receptors opened up a new avenue for pathophysiological research on this lipid mediator. Cellular and molecular in vitro studies and in vivo studies on gene deficient mice have elucidated cellular signaling pathways and the pathophysiological meanings of S1P receptors. Another unexpected finding that fingolimod (FTY720) modulates S1P receptors accelerated drug discovery in this field. Fingolimod was approved as a first-in-class, orally active drug for relapsing multiple sclerosis in 2010, and its applications in other disease conditions are currently under clinical trials. In addition, more selective S1P receptor modulators with better pharmacokinetic profiles and fewer side effects are under development. Some of them are being clinically tested in the contexts of multiple sclerosis and other autoimmune and inflammatory disorders, such as, psoriasis, Crohn’s disease, ulcerative colitis, polymyositis, dermatomyositis, liver failure, renal failure, acute stroke, and transplant rejection. In this review, the authors discuss the state of the art regarding the status of drug discovery efforts targeting S1P receptors and place emphasis on potential clinical applications.
Acute Kidney Injury ; Animals ; Clone Cells ; Cloning, Organism ; Colitis, Ulcerative ; Dermatomyositis ; Drug Discovery* ; Fingolimod Hydrochloride ; Graft Rejection ; In Vitro Techniques ; Liver Failure ; Mice ; Multiple Sclerosis ; Polymyositis ; Psoriasis ; Receptors, Lysosphingolipid* ; Second Messenger Systems ; Sphingosine* ; Stroke

A 46-year old woman presented with progressive limb weakness and fatigue. Laboratory tests showed abnormalities consistent with autoimmune hepatitis and she was diagnosed with biopsy-proven inflammatory myopathy. The patient was commenced on immunosuppressive therapy with azathioprine 50 mg and prednisolone 1 mg/kg. At the six-month follow up, her symptoms subsided and aminotransferase and muscle enzymes were normalized. This case presents rare case of concomitant development of polymyositis and autoimmune hepatitis.
Autoimmunity ; Azathioprine ; Extremities ; Fatigue ; Female ; Follow-Up Studies ; Hepatitis ; Hepatitis, Autoimmune* ; Humans ; Myositis ; Polymyositis* ; Prednisolone

Polymyositis (PM) is a chronic inflammatory disease that predominantly affects muscles. Systemic organ involvement, including the respiratory and gastrointestinal tracts, is frequently observed in PM, but renal involvement is rare. Herein, we report the case of a 56-year-old woman presenting with weight gain, edema, and generalized myalgia. Laboratory tests revealed elevated creatinine kinase level, hypoalbuminemia, and proteinuria. Histopathological examination of muscle biopsy revealed inflammatory myositis, and a renal biopsy confirmed immunoglobulin A (IgA) nephropathy. Based on the clinico-pathological results, the patient was diagnosed with PM with IgA nephropathy. This is a report of a rare occurrence of IgA nephropathy in a patient with PM presenting with chronic glomerulonephritis.
Biopsy ; Creatinine ; Edema ; Female ; Gastrointestinal Tract ; Glomerulonephritis ; Glomerulonephritis, IGA* ; Humans ; Hypoalbuminemia ; Immunoglobulin A* ; Immunoglobulins* ; Middle Aged ; Muscles ; Myalgia ; Myositis ; Phosphotransferases ; Polymyositis* ; Proteinuria ; Weight Gain

BACKGROUNDDermatomyositis (DM) and polymyositis (PM) are common inflammatory myopathies whose immunopathogenic mechanisms remain poorly understood. The NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome is a type of cytoplasmic multiprotein inflammasome and is responsible for the activation of inflammatory reactivations. Responding to a wide range of exogenous and endogenous microbial or sterile stimuli, NLRP3 inflammasomes can cleave pro-caspase-1 into active caspase-1, which processes the pro-inflammatory cytokines pro-interleukin (IL)-1β and pro-IL-18 into active and secreted IL-1β and IL-18. The NLRP3 inflammasome is implicated in infectious and sterile inflammatory diseases. However, it remains unclear whether it is involved in the pathogenesis of DM/PM, which we aim to address in our research.

METHODSIn this study, 22 DM/PM patients and 24 controls were recruited. The protein and RNA expression of IL-1β, IL-18, NLRP3, and caspase-1 in serum and muscle samples were tested and compared between the two groups.

RESULTSThe serum IL-1β and IL-18 levels were significantly higher in DM/PM patients than those in the controls by enzyme linked immunosorbent assay (ELISA, DM vs. control, 25.02 ± 8.29 ng/ml vs. 16.49 ± 3.30 ng/ml,P < 0.001; PM vs. control, 26.49 ± 7.79 ng/ml vs. 16.49 ± 3.30 ng/ml,P < 0.001). Moreover, the real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) showed that DM/PM patients exhibited higher RNA expression of IL-1β, IL-18, and NLRP3 in the muscle (for IL-1β, DM vs. control, P= 0.0012, PM vs. control, P= 0.0021; for IL-18, DM vs. control, P= 0.0045, PM vs. control, P= 0.0031; for NLRP3, DM vs. control, P= 0.0017, PM vs. control, P= 0.0006). Moreover, the protein expression of NLRP3 and caspase-1 in muscle samples of DM/PM patients were also significantly elevated compared to that in the muscles of the controls.

CONCLUSIONSOur findings demonstrate that the NLRP3 inflammasome is implicated in the pathogenesis of DM/PM. High NLRP3 expression led to elevated levels of IL-1β and IL-18 and could be one of the factors promoting disease progress.

Adult ; Caspase 1 ; analysis ; genetics ; Dermatomyositis ; etiology ; Female ; Humans ; Inflammasomes ; physiology ; Interleukin-18 ; analysis ; genetics ; Interleukin-1beta ; analysis ; genetics ; Male ; Middle Aged ; NLR Family, Pyrin Domain-Containing 3 Protein ; analysis ; genetics ; physiology ; Polymyositis ; etiology

Antisynthetase syndrome has been recognized as an important cause of autoimmune inflammatory myopathy in a subset of patients with polymyositis and dermatomyositis. It is associated with serum antibody to aminoacyl-transfer RNA synthetases and is characterized by a constellation of manifestations, including fever, myositis, interstitial lung disease, mechanic's hand-like cutaneous involvement, Raynaud phenomenon, and polyarthritis. Lung disease is the presenting feature in 50% of the cases. We report a case of a 60-year-old female with acute respiratory distress syndrome (ARDS), which later proved to be an unexpected and initial manifestation of anti-Jo-1 antibody-positive antisynthetase syndrome. The present case showed resolution of ARDS after treatment with high-dose corticosteroids. Given that steroids are not greatly beneficial in the treatment of ARDS, it is likely that the improvement of the respiratory symptoms in this patient also resulted from the prompt suppression of the inflammatory systemic response by corticosteroids.
Adrenal Cortex Hormones ; Arthritis ; Dermatomyositis ; Female ; Fever ; Humans ; Immunoglobulins ; Ligases ; Lung Diseases ; Lung Diseases, Interstitial ; Middle Aged ; Myositis ; Polymyositis ; Raynaud Disease ; Respiratory Distress Syndrome, Adult* ; RNA ; Steroids