Autoimmune muscle disease

Autoantibody evaluation in idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIM), generally referred to as myositis is a heterogeneous group of diseases characterized by muscle inflammation and/or skin involvement, diverse extramuscular manifestations with variable risk for malignancy and response to treatment. Contemporary clinico-serologic categorization identifies 5 main clinical groups which can be further stratified based on age, specific clinical manifestations and/or risk for cancer. The serological biomarkers for this classification are generally known as myositis-specific (MSAs) and myositis-associated antibodies. Based on the use of these antibodies, IIM patients are classified into anti-synthetase syndrome, dermatomyositis, immune-mediated necrotizing myopathy, inclusion body myositis, and overlap myositis. The current classification criteria for IIM requires clinical findings, laboratory measurements, and histological findings of the muscles. However, the use MSAs and myositis-associated autoantibodies as an adjunct for disease evaluation is thought to provide a cost-effective personalized approach that may not only guide diagnosis but aid in stratification and/or prognosis of patients. This review provides a comprehensive overview of contemporary autoantibodies that are specific or associated myositis. In addition, it highlights possible pathways for the detection and interpretation of these antibodies with limitations for routine clinical use.

Evaluation of the effectiveness of using prednisolone, tacrolimus, and intravenous immunoglobulin combination therapy on immune-mediated necrotizing myopathy-A non-randomized, observational research

OBJECTIVE

To recruit immune-mediated necrotizing myopathy (IMNM) patients with extramuscular manifestations who were refractory to initial therapy with either monotherapy with prednisolone or dual therapy with prednisolone and immunosuppressants. These patients subsequently received a combination of prednisolone, tacrolimus, and intravenous immunoglobulin (IVIG), and the efficacy of this treatment regimen was assessed in patients with IMNM.

METHOD

①Clinical data and treatment measures are as follows: This study enrolled IMNM patients who were treated at the Neurology Department of the First Medical Center of PLA General Hospital from April 2020 to May 2023. These patients received a combination therapy of prednisolone, tacrolimus, and IVIG. ②Observational indicators included manual muscle test for 8 groups of muscles (MMT-8), muscle enzyme levels (creatine kinase (CK), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST)), and myositis disease activity assessment tool (MDAAT).

RESULTS

This study enrolled eight patients. All observational indicators declined after treatment compared to before treatment, and these changes were statistically significant. Moreover, extramuscular manifestations also ameliorated compared to before treatment.

CONCLUSION

The combination therapy of prednisolone, tacrolimus, and IVIG has demonstrated favorable efficacy in IMNM and broadened the treatment options for this disease. However, the results still require further validation by large-scale and randomized controlled studies.

Clinical and pathological features of immune-mediated necrotising myopathies in a single-centre muscle biopsy cohort

Objective

Immune-mediated necrotising myopathy (IMNM) is a subset of idiopathic inflammatory myopathies (IIM) characterized by significantly elevated creatine kinase level, muscle weakness and predominant muscle fibre necrosis in muscle biopsy. This study aimed to investigate the clinical and pathological characteristics of patients with IMNM in a single-centre muscle biopsy cohort.

Methods

A total of 860 patients who had muscle biopsy reports in our centre from May 2008 to December 2017 were enrolled in this study. IMNM was diagnosed according to the 2018 European Neuromuscular Centre (ENMC) clinicopathological diagnostic criteria for IMNM.

Results

The muscle biopsy cohort consisted of 531 patients with IIM (61.7%), 253 patients with non-IIM (29.4%), and 76 undiagnosed patients (8.8%). IIM cases were classified as IMNM (68[7.9%]), dermatomyositis (346[40.2%]), anti-synthetase syndrome (82[9.5%]), polymyositis (32[3.7%]), and sporadic inclusion body myositis (3[0.3%]). Limb girdle muscular dystrophy (LGMD) 2B and lipid storage myopathy (LSM) are the two most common non-IIM disorders in our muscle biopsy cohort. IMNM patients had a higher onset age (41.57 ± 14.45 vs 21.66 ± 7.86 and 24.56 ± 10.78, p < .0001), shorter duration (21.79 ± 26.01 vs 66.69 ± 67.67 and 24.56 ± 10.78, p < .0001), and more frequent dysphagia (35.3% vs. 3.4 and 6.3%, p = .001) than LGMD 2B and LSM patients. Muscle biopsy from IMNM showed more frequent muscle fibre necrosis (95.6% vs 72.4 and 56.3%, p < .0001), overexpression of major histocompatibility complex-I on sarcolemma (83.8% vs 37.9 and 12.9%, p < .0001), and CD4⁺ T cell endomysia infiltration (89.7% vs 53.6 and 50%, p < .0001) compared with those from LGMD 2B and LSM patients.

Conclusions

It is easy to distinguish IMNM from other IIM subtypes according to clinical symptoms and myositis specific antibodies profiles. However, distinguishing IMNM from disorders clinically similar to non-IIM needs combined clinical, serological and pathological features.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05372-z.

Therapeutic management of immune-mediated necrotizing myositis

Purpose of Review

The idiopathic inflammatory myopathies are a heterogeneous group of autoimmune disorders characterized by skeletal muscle inflammation leading to chronic muscle weakness. Immune-mediated necrotizing myopathy (IMNM) is a distinct subgroup of inflammatory myopathy typically characterized by myofiber necrosis with minimal inflammatory infiltrates on muscle biopsy, highly elevated creatine kinase levels, and infrequent extra-muscular involvement. This review provides an overview of currently recommended treatment strategies for IMNM, including discussion of disease activity monitoring and recommended first-line immunomodulatory agents depending on clinical phenotype and autoantibody status.

Recent Findings

IMNM can be divided into three subtypes based on autoantibody positivity: anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) IMNM, anti-signal recognition particle (SRP) IMNM, and antibody negative IMNM. Autoantibody status in IMNM has considerable correlation with clinical phenotype, prognosis, and recommended choice of immunosuppressive agent. Patients with anti-HMGCR IMNM tend to respond well to intravenous immunoglobulin (IVIG), and IVIG monotherapy may be sufficient treatment for certain patients. In anti-SRP IMNM, early rituximab is commonly favored. More generally, prompt initiation of aggressive immunosuppression is often indicated, as both anti-SRP and anti-HMGCR IMNM can potentially cause debilitating weakness, and muscle atrophy and irreversible fatty replacement happen early in the disease course. Patients with IMNM frequently require combination therapy to achieve disease control, and have a high rate of relapse when tapering immunosuppression. Young age of onset is a poor prognostic factor.

Summary

IMNM can be severely disabling and often requires aggressive immunosuppression. For any given patient, the treatment strategy should be informed by the severity of their presenting features and autoantibody status. While our ability to treat IMNM has certainly improved, there remains a need for more prospective trials to inform optimal treatment strategies.

Dysthyroidism in dermato/polymyositis patients: A case-control study

BACKGROUND

Dermatomyositis (DM) and polymyositis (PM) are two rare autoimmune disorders occasionally described with dysthyroidism; however, no solid evidence still proves such an association.

AIM

To evaluate the prevalence of dysthyroidism among DM/PM patients.

DESIGN AND SETTING

A nation-wide case-control study was conducted.

METHODS

From the Clalit Health Services health records database, we extracted 2085 (DM = 1475 (70.7%), PM = 610 (29.3%)) PM/DM cases and 10 193 sex-age matched controls in the period 2000-2018. Both univariate and multivariate analyses were performed to evaluate the link dysthyroidism and PM/DM. Survival analysis was also performed.

RESULTS

The rate of hyperthyroidism was significantly (P = .0097) higher in cases (n = 40, 1.9%) with respect to controls (n = 123, 1.2%). Similarly, the rate of hypothyroidism was significantly (P < .0001) associated with cases (n = 234, 11.2%) when compared to controls (n = 853, 8.4%). At the multivariate logistic regression analysis, both DM (OR 1.31 [95%CI 1.07-1.60], P = .0087) and PM (OR 1.54 [95%CI 1.21-1.95], P = .004) were significantly associated with hypothyroidism, whereas DM (OR 1.70 [95%CI 1.10-2.61], P = .0165) but not PM (OR 1.45 [0.83-2.55], P = .1947) was found to be associated with hyperthyroidism. Subjects with PM and positive for anti-Sjögren's syndrome-related antigen A (SSA) auto-antibody displayed a significant risk of developing hyperthyroidism (OR 5.85 [95%CI 1.02-33.74], P = .0480), whereas individuals with DM and positive for antinuclear antibody (ANA) had a higher risk of developing hyperthyroidism (OR 2.65 [95%CI 1.00-7.03], P = .0498).

CONCLUSIONS

Physicians treating PM/DM patients should consider screening for thyroid dysfunction on a regular basis.

Immune myopathy with large histiocyte-related myofiber necrosis

OBJECTIVE

To describe the features of a new, pathologically distinctive, acquired myopathy with an unusual pattern of scattered necrotic muscle fibers that are neighbored, surrounded, or invaded, by large, often multinucleated, histiocytic cells.

METHODS

Retrospective review of records and muscle pathology of 4 patients.

RESULTS

Clinical features common to our patients included muscle pain and proximal, symmetric, moderate to severe, weakness in the arms and legs progressing over 1-4 weeks. Patients had other associated systemic disorders, including anemia in all, and hemophagocytic lymphohistiocytosis, hepatic disease, Raynaud phenomenon, metastatic cancer, and cardiomyopathy, in 1 patient each. Serum creatine kinase (CK) levels at presentation were very high, ranging from 10,000 to 102,000 U/L. Three patients improved within 3 months after treatment. Muscle pathology included scattered necrotic muscle fibers with cytoplasm that stained for C_5b-9 complement, especially around fiber peripheries, pale on nicotinamide adenine dinucleotide and often dark on hematoxylin & eosin. Large, often multinucleated, cells with features of histiocytes, including anatomical features on electron microscopy and immunostaining for major histocompatibility complex Class I and histiocyte markers (HAM56, CD68, CD163, and S100), were usually closely apposed to the surface of, or invaded, necrotic myofibers.

CONCLUSIONS

Patients with large-histiocyte-associated myopathy (LHIM) had a subacute onset of proximal predominant weakness, associated systemic disorders, very high serum CK, and a pathologically distinctive pattern of large histiocyte-associated muscle fiber necrosis. LHIM may be caused by an autoimmune, histiocyte-mediated attack directed against muscle fibers.

Autoimmune Myopathies: Updates on Evaluation and Treatment

The major forms of autoimmune myopathies include dermatomyositis (DM), polymyositis (PM), myositis associated with antisynthetase syndrome (ASS), immune-mediated necrotizing myopathy (IMNM), and inclusion body myositis (IBM). While each of these conditions has unique clinical and histopathological features, they all share an immune-mediated component. These conditions can occur in isolation or can be associated with systemic malignancies or connective tissue disorders (overlap syndromes). As more has been learned about these conditions, it has become clear that traditional classification schemes do not adequately group patients according to shared clinical features and prognosis. Newer classifications are now utilizing myositis-specific autoantibodies which correlate with clinical and histopathological phenotypes and risk of malignancy, and help in offering prognostic information with regard to treatment response. Based on observational data and expert opinion, corticosteroids are considered first-line therapy for DM, PM, ASS, and IMNM, although intravenous immunoglobulin (IVIG) is increasingly being used as initial therapy in IMNM related to statin use. Second-line agents are often required, but further prospective investigation is required regarding the optimal choice and timing of these agents.

Multiple values of 18F-FDG PET/CT in idiopathic inflammatory myopathy

This study aimed to investigate the multiple values of ¹⁸F-FDG PET/CT in detecting malignant tumors, evaluating myopathy, and determining interstitial lung disease in patients with idiopathic inflammatory myopathy (IIM). We retrospectively analyzed the data of 38 patients who were examined by ¹⁸F-FDG PET/CT and eventually diagnosed as IIM. We also collected the data of another 22 cases with negative PET/CT as the control. Pulmonary HRCT images were acquired simultaneously with regular ¹⁸F-FDG PET/CT imaging for each patient. Image analysis included the presence of malignant lesions, muscular FDG uptake, and interstitial lung disease and its imaging features. IIM was classified into polymyositis (PM), classic dermatomyositis (CDM), and clinical amyopathic dermatomyositis (CADM). All suspected malignant lesions were confirmed by histopathological examination. Interstitial lung disease was diagnosed by HRCT. Rapidly progressive interstitial lung disease (RP-ILD) was determined according to clinical follow-ups. The significance of ¹⁸F-FDG PET/CT in the detection of malignancy, observation of activity of myopathy, and determination of interstitial lung disease in IIM patients was explored based on the final clinical diagnosis. In the 38 patients with IIM, 3 cases were classified as PM, 18 as CDM, and 17 as CADM. PET/CT correctly detected 7 cases (18.4%) of malignant tumors, and all of which were found in CDM and PM patients. The muscular FDG uptake in IIM patients was higher than the control population, and it was higher in patients with myopathy (including PM and CDM) than in patients with CADM. The muscular FDG uptake in IIM patients was correlated with elevated serum creatine kinase level (r = 0.332, P = 0.042) and impaired muscle strength (r = -0.605, P < 0.001). Interstitial lung disease was detected by HRCT in 30 patients (78.9%), and 7 of them were eventually confirmed as RP-ILD, according to the clinical outcome. The FDG uptake in lung lesions of RP-ILD patients was higher than those with chronic interstitial lung diseases, even though no significant difference was found between the CT features of RP-ILD and chronic interstitial lung disease. When SUV_max ≥ 2.4 was employed as the threshold for RP-ILD prediction, the diagnostic efficiency was yield with a sensitivity of 100.0% (7/7), specificity of 87.0% (20/23), and accuracy of 90.0% (27/30), respectively. For IIM patients, ¹⁸F-FDG PET/CT has multiple values in identifying malignancies, observing the status of inflammatory myopathy, detecting interstitial lung disease, and predicting the occurrence of RP-ILD. Therefore, it is recommended to use PET/CT in the clinical course of diagnosis and management of IIM.