Fasciitis as a common lesion of dermatomyositis, demonstrated early after disease onset by en bloc biopsy combined with magnetic resonance imaging

Anti-NXP2 Antibody-positive Juvenile Dermatomyositis with Characteristic Fascial Thickening on Muscle Ultrasound and Improvement with Immunotherapy

We herein report a 12-year-old boy who presented with a fever, erythematous rash on the cheeks, back pain, and dysphagia. Blood tests revealed increased creatine kinase levels, and muscle ultrasonography (MUS) revealed characteristic fascial thickening in the lumbar paraspinal muscles, where myalgia was prominent. Sarcoplasmic expression of myxovirus-resistant protein A on a muscle biopsy and the presence of anti-nuclear matrix protein 2 (NXP2) antibodies confirmed the diagnosis of dermatomyositis. Prednisolone and intravenous immunoglobulin therapy improved the clinical and laboratory parameters as well as fascial thickening. MUS is useful for evaluating fasciitis associated with anti-NXP2 autoantibodies and monitoring therapeutic efficacy.

[Expert recommendations for magnetic resonance imaging of muscle disorders]

BACKGROUND

Magnetic resonance (MRI) imaging of the skeletal muscles (muscle MRI for short) is increasingly being used in clinical routine for diagnosis and longitudinal assessment of muscle disorders. However, cross-centre standards for measurement protocol and radiological assessment are still lacking.

OBJECTIVES

The aim of this expert recommendation is to present standards for the application and interpretation of muscle MRI in hereditary and inflammatory muscle disorders.

METHODS

This work was developed in collaboration between neurologists, neuroradiologists, radiologists, neuropaediatricians, neuroscientists and MR physicists from different university hospitals in Germany. The recommendations are based on expert knowledge and a focused literature search.

RESULTS

The indications for muscle MRI are explained, including the detection and monitoring of structural tissue changes and oedema in the muscle, as well as the identification of a suitable biopsy site. Recommendations for the examination procedure and selection of appropriate MRI sequences are given. Finally, steps for a structured radiological assessment are presented.

CONCLUSIONS

The present work provides concrete recommendations for the indication, implementation and interpretation of muscle MRI in muscle disorders. Furthermore, it provides a possible basis for the standardisation of the measurement protocols at all clinical centres in Germany.

[Expert recommendations for magnetic resonance imaging of muscle disorders]

BACKGROUND

Magnetic resonance (MRI) imaging of the skeletal muscles (muscle MRI for short) is increasingly being used in clinical routine for diagnosis and longitudinal assessment of muscle disorders. However, cross-centre standards for measurement protocol and radiological assessment are still lacking.

OBJECTIVES

The aim of this expert recommendation is to present standards for the application and interpretation of muscle MRI in hereditary and inflammatory muscle disorders.

METHODS

This work was developed in collaboration between neurologists, neuroradiologists, radiologists, neuropaediatricians, neuroscientists and MR physicists from different university hospitals in Germany. The recommendations are based on expert knowledge and a focused literature search.

RESULTS

The indications for muscle MRI are explained, including the detection and monitoring of structural tissue changes and oedema in the muscle, as well as the identification of a suitable biopsy site. Recommendations for the examination procedure and selection of appropriate MRI sequences are given. Finally, steps for a structured radiological assessment are presented.

CONCLUSIONS

The present work provides concrete recommendations for the indication, implementation and interpretation of muscle MRI in muscle disorders. Furthermore, it provides a possible basis for the standardisation of the measurement protocols at all clinical centres in Germany.

The value of non-enhanced MRI in the evaluation of patients with suspected idiopathic inflammatory myopathy

INTRODUCTION/AIMS

The performance of magnetic resonance imaging (MRI) for diagnosing suspected idiopathic inflammatory myopathy (IIM) remains controversial. Furthermore, the role of contrast-enhanced magnetic resonance imaging (CE-MRI) sequences is unclear. The aim of this study was to evaluate the sensitivity and specificity of a non-enhanced magnetic resonance imaging (NE-MRI) protocol compared to a CE-MRI protocol in adult patients with confirmed IIM.

METHODS

This study retrospectively enrolled patients with suspected IIM who underwent MRI of the upper thigh between 2008 and 2020. The protocol consisted of a T1-weighted (T1w) sequence, a turbo inversion recovery magnitude (TIRM) sequence and a contrast-enhanced T1-weighted sequence (CE-T1w). After randomly stratifying patients into a group with only the T1w and TIRM sequences available and another group with additional availability of CE-T1w, three blinded readers assessed the presence of IIM based on characteristic imaging features. Confirmation of the diagnosis was determined based on the 2017 ACR/EULAR criteria.

RESULTS

Of the 80 patients (mean age 49.0 ± 21.1 years; 42 female, 38 male) included, 54 (67.5%) had a positive diagnosis of IIM. Cumulated sensitivity and specificity for MRI to detect IIM was 87.1% and 83.3% in the NE-MRI group versus 87.0% and 63.0% in the CE-MRI group. The group differences for sensitivity and specificity were non-significant for each of the three readers, respectively (p ≥ .081).

DISCUSSION

NE-MRI detects suspected IIM with high diagnostic accuracy and performs equivalently to CE-MRI. Therefore, it may be appropriate to omit the use of contrast agents in MRI scans performed for suspected IIM.

Myofascial edema of gastrocnemius: A prominent MRI characteristic in dermatomyositis patients with anti-transcriptional intermediate factor 1-γ antibody

AIMS

This study was designed to evaluate the magnetic resonance imaging (MRI) patterns of the lower limb muscles in dermatomyositis (DM) with anti-transcriptional intermediate factor 1-γ (anti-TIF1-γ) antibody.

METHODS

This retrospective, observational, cross-sectional study enrolled 12 adult DM patients with anti-TIF1-γ antibody. Muscles were assessed for fascial edema, subcutaneous-tissue edema, muscle edema, and fatty replacement. These features were analyzed in relation to clinical characteristics.

RESULTS

All 12 patients underwent hip and thigh MRI, and 8 completed calf MRI. All patients showed myofascial edema, muscle edema, and fatty replacement, and 8 out of 12 further exhibited subcutaneous-tissue edema. Specifically, myofascial edema of the gastrocnemius was observed in all patients (8/8). The vastus intermedialis and vastus lateralis muscles showed the most severe muscle edema, whereas the caput breve of the biceps femoris, semitendinosus, and soleus muscles exhibited the most severe fatty replacement. Although only 1 patient exhibited asymmetric muscle weakness, 9 showed asymmetric muscle edema, and 10 showed asymmetric fatty replacement. Changes in muscle edema positively correlated with creatine kinase (CK) levels.

CONCLUSIONS

Myofascial edema of gastrocnemius was a prominent characteristic of anti-TIF1-γ-positive DM. Early detection of muscle edema, as well as CK levels, may be helpful for monitoring disease activity.

255th ENMC workshop: Muscle imaging in idiopathic inflammatory myopathies. 15th January, 16th January and 22nd January 2021 - virtual meeting and hybrid meeting on 9th and 19th September 2022 in Hoofddorp, The Netherlands

The 255th ENMC workshop on Muscle Imaging in Idiopathic Inflammatory myopathies (IIM) aimed at defining recommendations concerning the applicability of muscle imaging in IIM. The workshop comprised of clinicians, researchers and people living with myositis. We aimed to achieve consensus on the following topics: a standardized protocol for the evaluation of muscle images in various types of IIMs; the exact parameters, anatomical localizations and magnetic resonance imaging (MRI) techniques; ultrasound as assessment tool in IIM; assessment methods; the pattern of muscle involvement in IIM subtypes; the application of MRI as biomarker in follow-up studies and clinical trials, and the place of MRI in the evaluation of swallowing difficulty and cardiac manifestations. The following recommendations were formulated: In patients with suspected IIM, muscle imaging is highly recommended to be part of the initial diagnostic workup and baseline assessment. MRI is the preferred imaging modality due to its sensitivity to both oedema and fat accumulation. Ultrasound may be used for suspected IBM. Repeat imaging should be considered if patients do not respond to treatment, if there is ongoing diagnostic uncertainty or there is clinical or laboratory evidence of disease relapse. Quantitative MRI is established as a sensitive biomarker in IBM and could be included as a primary or secondary outcome measure in early phase clinical trials, or as a secondary outcome measure in late phase clinical trials. Finally, a research agenda was drawn up.

Intramuscular lesions in musculoskeletal MRI as a favourable prognostic sign in patients with anti-MDA5 antibody-positive dermatomyositis

OBJECTIVES

Anti-differentiation-associated gene 5 (MDA5) antibody-positive dermatomyositis, which has been described as clinically amyopathic dermatomyositis, complicates rapidly progressive interstitial lung disease (ILD). Owing to the absence of significant muscle symptoms, musculoskeletal MRI is often not performed. In this study, we aimed to devise a simple evaluation method using musculoskeletal MRI findings to elucidate the relationship between MRI findings and ILD prognosis and development.

METHODS

The medical records and MRI scans of the proximal muscles at the time of diagnosis were retrospectively reviewed for 28 patients with anti-MDA5 antibody-positive dermatomyositis who were admitted to The Jikei University Hospital and The Jikei University Kashiwa Hospital between January 2008 and March 2022. Three observers evaluated nine proximal muscles for high signals on either short-tau inversion recovery images and/or fat-saturated gadolinium-enhanced T1-weighted images in the fascia and/or in the margins of the muscles in contact with the fascia (fascial pattern), and/or high signals in the muscles away from the fascia (intramuscular pattern), and a consensus was reached.

RESULTS

Of the 28 patients, 15 presented with 'radiological myositis', where an intramuscular pattern was observed at any site. Patients with radiological myositis had significantly higher survival rates than those without radiological myositis, despite the lower rate of triple therapy with prednisolone, calcineurin inhibitors and cyclophosphamide. The spread of ILD on chest CT negatively and significantly correlated with the proportion of intramuscular lesions.

CONCLUSION

The detection of intramuscular lesions on musculoskeletal MRI using our novel evaluation method could be clinically useful as a favourable prognostic marker.

Ultrasound and MR muscle imaging in new onset idiopathic inflammatory myopathies at diagnosis and after treatment: a comparative pilot study

OBJECTIVES

To prospectively compare ultrasound (US) and whole-body MRI for detection of muscle abnormalities compatible with idiopathic inflammatory myopathies (IIM).

METHODS

Newly diagnosed IIM patients underwent US (14 muscles) and MRI (36 muscles) at diagnosis and after nine weeks monotherapy with intravenous immunoglobulin. Muscles were compatible with IIM when quantitative US echo-intensity (EI) z scores was ≥1.5, semi-quantitative US Heckmatt score was ≥2, qualitative US was abnormal, or when MRI showed oedema on T2-weighted images. At patient level, findings were classified as abnormal when quantitative US EI z scores was >1.5 (n = 3 muscles), >2.5 (n = 2 muscles) or >3.5 (n = 1 muscle), or if ≥3 muscles showed abnormalities as described above for the other diagnostic methods.

RESULTS

At diagnosis, in 18 patients US of 252 muscles revealed abnormalities in 36 muscles (14%) with quantitative, in 153 (61%) with semi-quantitative and in 168 (67%) with qualitative analysis. MRI showed oedema in 476 out of 623 muscles (76%). Five patients (28%) reached abnormal classification with quantitative US, 16 (89%) with semi-quantitative and qualitative US, and all patients (100%) with MRI. Nine-week follow-up of 12 patients showed no change over time with quantitative US or MRI, and a decrease in abnormalities with semi-quantitative US (P <0.01), and qualitative US (P <0.01).

CONCLUSION

At diagnosis, MRI was more sensitive than US to detect muscle abnormalities compatible with IIM. Semi-quantitative US and qualitative US detected abnormalities in the majority of the patients while evaluating fewer muscles than MRI and showed change over time after nine weeks of treatment.

Physical Characteristics of Injection Site Pain After COVID-19 mRNA BNT162b2 Vaccination

Background

BNT162b2, an mRNA COVID-19 vaccine, was launched in many countries as an intramuscular vaccination for COVID-19 infection. Few studies have assessed the physical indications of pain at the immunization site. This study aimed to characterize pain at the injection site and investigate morphological attributes using ultrasound.

Methods

Forty-three of 211 healthcare workers who received a second dose of BNT162b2 between February 2021 and March 2021 were enrolled in the study. The mean age of the subjects was 40 years. We evaluated patients' pain at the injection site using the Numerical Rating Pain Scale (NRPS). We also assessed the thickness of the deltoid muscle fascia at the injection site by ultrasound. Bayesian robust correlation was employed to explore the relationship between the pain intensity scores and ultrasound measurements.

Results

All eligible subjects complained of pain at the injection site. A median pain onset of 8 hours post-vaccination and a median peak intensity score of 4 were reported. Onset of relief occurred after 2 days. Ultrasound images demonstrated a 2.5-fold increase in fascia thickness at the injection site without intramuscular echogenicity change in all subjects. A correlation was established between the NRPS score and the non-injection-to-injection-side ratio of fascia thickness at the injection site (rho = 0.66).

Conclusion

A sore arm was the most prevalent side effect of BNT162b2 vaccination and could be attributed to temporal fasciitis.

Dermatomyositis: Patterns of MRI findings in muscles, fascia and skin of pelvis and thigh

PURPOSE

This review discusses characteristic, subtle, and florid changes in muscle, fascia, skin, and subcutaneous tissue of the lower limbs in MR imaging in patients with dermatomyositis.

MATERIAL AND METHODS

This review is based on the analysis of 43 patients with dermatomyositis who were imaged from January 2014 to March 2021 in our institute as well a critical review of literature of MRI in dermatomyositis.

RESULTS

Muscle involvement is predominantly bilaterally symmetric and involves anterior, posterior as well as medial compartments of the thigh. Diffuse intramuscular hyperintensity on T2-weighted images is a common pattern of involvement. Isolated myofascial involvement or muscular with myofascial involvement can also occur. Nodular areas of hyper intensity and enhancement is another uncommon pattern of muscle involvement. Reticular pattern of subcutaneous tissue involvement and skin thickening is best seen on fat saturated T2 -weighted images. Calcification in the subcutaneous tissues appears hypointense with a surrounding hyperintense rim on all pulse sequences which shows peripheral enhancement. MRI patterns of involvement range from subtle myofascial and skin involvement to florid muscular involvement. Diffusion weighted imaging is useful for myofascial involvement. Whole body MR can detect changes at unusual sites in muscles and extra skeletal involvement. Contrast enhanced imaging has no added benefit. Treatment responders show a return to normal signal intensity on MRI.

CONCLUSION

This review highlights the patterns of muscle, skin, and subcutaneous tissue involvement of thighs in dermatomyositis on conventional MRI and the role of whole-body MR, diffusion weighted imaging and limited role of contrast enhanced imaging.

MRI and muscle imaging for idiopathic inflammatory myopathies

Although idiopathic inflammatory myopathies (IIM) are a heterogeneous group of diseases nearly all patients display muscle inflammation. Originally, muscle biopsy was considered as the gold standard for IIM diagnosis. The development of muscle imaging led to revisiting not only the IIM diagnosis strategy but also the patients' follow-up. Different techniques have been tested or are in development for IIM including positron emission tomography, ultrasound imaging, ultrasound shear wave elastography, though magnetic resonance imaging (MRI) remains the most widely used technique in routine. Whereas guidelines on muscle imaging in myositis are lacking here we reviewed the relevance of muscle imaging for both diagnosis and myositis patients' follow-up. We propose recommendations about when and how to perform MRI on myositis patients, and we describe new techniques that are under development.

Texture analysis of muscle MRI: machine learning-based classifications in idiopathic inflammatory myopathies

To develop a machine learning (ML) model that predicts disease groups or autoantibodies in patients with idiopathic inflammatory myopathies (IIMs) using muscle MRI radiomics features. Twenty-two patients with dermatomyositis (DM), 14 with amyopathic dermatomyositis (ADM), 19 with polymyositis (PM) and 19 with non-IIM were enrolled. Using 2D manual segmentation, 93 original features as well as 93 local binary pattern (LBP) features were extracted from MRI (short-tau inversion recovery [STIR] imaging) of proximal limb muscles. To construct and compare ML models that predict disease groups using each set of features, dimensional reductions were performed using a reproducibility analysis by inter-reader and intra-reader correlation coefficients, collinearity analysis, and the sequential feature selection (SFS) algorithm. Models were created using the linear discriminant analysis (LDA), quadratic discriminant analysis (QDA), support vector machine (SVM), k-nearest neighbors (k-NN), random forest (RF) and multi-layer perceptron (MLP) classifiers, and validated using tenfold cross-validation repeated 100 times. We also investigated whether it was possible to construct models predicting autoantibody status. Our ML-based MRI radiomics models showed the potential to distinguish between PM, DM, and ADM. Models using LBP features provided better results, with macro-average AUC values of 0.767 and 0.714, accuracy of 61.2 and 61.4%, and macro-average recall of 61.9 and 59.8%, in the LDA and k-NN classifiers, respectively. In contrast, the accuracies of radiomics models distinguishing between non-IIM and IIM disease groups were low. A subgroup analysis showed that classification models for anti-Jo-1 and anti-ARS antibodies provided AUC values of 0.646–0.853 and 0.692–0.792, with accuracy of 71.5–81.0 and 65.8–78.3%, respectively. ML-based TA of muscle MRI may be used to predict disease groups or the autoantibody status in patients with IIM and is useful in non-invasive assessments of disease mechanisms.

Diagnostic value of additional histopathological fascia examination in idiopathic inflammatory myopathies

Background and purpose

Correct diagnosis of idiopathic inflammatory myopathies (IIM) may prevent harm from both lack of treatment in IIM patients and unnecessary treatment in non‐IIM patients. However, it is unknown whether additional histopathological fascia examination may contribute to diagnosing IIM.

Methods

Thirty‐two magnetic resonance imaging guided en bloc biopsies from patients diagnosed with IIM (except inclusion body myositis) from 2010 to 2017 were reviewed: dermatomyositis (DM) (n = 6), non‐specific/overlap myositis (NM/OM) (n = 11), immune‐mediated necrotizing myopathy (n = 12) and anti‐synthetase syndrome (n = 3). Muscle biopsy specimens were examined according to the 2004 European Neuromuscular Centre (ENMC) criteria. Fascia was subsequently examined for the presence of lymphocytic infiltrates. Isolated fascia involvement was defined as the presence of lymphocytic infiltrates in the fascia/epimysium on histopathology in the absence of any ENMC muscle histopathology/immunohistochemistry criteria.

Results

One patient with DM (17%) and one patient with NM/OM (9%) had isolated fascia involvement. One patient with immune‐mediated necrotizing myopathy (8%) and one patient with anti‐synthetase syndrome (33%) had fascia involvement, albeit in combination with muscle involvement.

Conclusion

Histopathological fascia examination may contribute to early diagnosis of DM and NM/OM in a small proportion of patients.

MRI of skeletal muscles in patients with idiopathic inflammatory myopathies: characteristic findings and diagnostic performance in dermatomyositis

Objective

To define the characteristic findings on MRI of skeletal muscles in patients with dermatomyositis (DM) relative to those in patients with other idiopathic inflammatory myopathies (IIMs) and to assess their diagnostic performance in DM.

Methods

Thirty-six patients with DM, 17 patients with amyopathic DM, 19 patients with polymyositis and 16 patients with non-IIM classified by the 2017 European League Against Rheumatism/American College of Rheumatology criteria were included in this study. The following MRI findings (short-tau inversion recovery [STIR] and gadolinium-enhanced fat-suppressed T1-weighted imaging [Gd-T1WI]) for proximal limb muscles were compared between the disease groups and between myositis-specific autoantibodies/myositis-associated autoantibodies (MSAs/MAAs)-positive and MSAs/MAAs-negative groups: structures with high signal intensity (HSI) (subcutaneous, fascia, muscle); distributions of HSI areas in muscle (diffuse, patchy, peripheral) and patterns of HSI in muscle (honeycomb, foggy, strong HSI). Univariate, multivariate and receiver-operating characteristic [ROC] analyses were performed to assess the diagnostic performance of MRI in DM.

Results

The characteristic MRI findings in patients with DM were subcutaneous HSI, fascial HSI, peripheral distribution and honeycomb pattern. The MRI findings in the MSAs/MAAs-positive group included more frequent fascial HSI but less frequent foggy pattern compared with the MSAs/MAAs-negative group. Likelihood of DM score ≥ 3 (obtained by counting the number of characteristic MRI findings in patients with DM) showed good diagnostic performance in DM (STIR: sensitivity 72.2%, specificity 88.5%, area under ROC curve [AUC] 84.9%; Gd-T1WI: sensitivity 81.2%, specificity 91.5%, AUC 89.9%).

Conclusion

The characteristic MRI findings of skeletal muscles can predict patients with DM as well as patients with MSAs/MAAs.

Current diagnosis and treatment of polymyositis and dermatomyositis

Idiopathic inflammatory myopathies (IIMs) are heterogeneous disorders that affect the skeletal muscles. Polymyositis, dermatomyositis, and inclusion body myositis are major IIM subsets. Immune-mediated necrotizing myopathy became recognized as a potentially new IIM subset. Since the new classification criteria published by the International Myositis Classification Criteria Project have higher sensitivity and specificity for IIM classification and subclassification than the previous criteria, they should help precise diagnosis. It should be noted that several tests available in current clinical practice, such as electromyography, magnetic resonance imaging, and other myositis-specific autoantibodies than anti-Jo-1 antibodies, were not included in the new criteria. As for treatment, glucocorticoids are used empirically as the first-line treatment despite their various adverse effects. Concomitant treatment with steroid-sparing immunosuppressive agents, including methotrexate, azathioprine, calcineurin inhibitors, mycophenolate mofetil, and cyclophosphamide, reduces successfully initial glucocorticoid doses for the remission induction, the relapse risk during glucocorticoid tapering, and adverse effects of glucocorticoids. Treatment with biologics, including rituximab and abatacept, seems promising in some IIM patients. Multi-target treatment with glucocorticoids and several steroid-sparing immunosuppressive agents is effective in refractory IIM patients. Considering proven steroid-sparing efficacy and tolerability of multi-target treatment in patients with other autoimmune diseases, it should be a good therapeutic option for IIMs.

Angiogenesis and VEGF-expressing cells are identified predominantly in the fascia rather than in the muscle during the early phase of dermatomyositis

Background

We previously demonstrated that fasciitis is a common lesion in dermatomyositis (DM) and that DM-associated fasciitis is detectable, as the result of the increased vascularity in the fascia, by power Doppler ultrasonography. We aimed to investigate whether angiogenesis and vascular endothelial growth factor (VEGF)-expressing cells in the fascia are histologically demonstrated during the early phase of DM, and whether inflammation is involved in angiogenesis and an increased number of VEGF-expressing cells.

Methods

We prospectively evaluated 22 patients with DM and 11 patients with polymyositis (PM). Immunohistochemical staining for CD31, VEGF, and tumor necrosis factor-α (TNF-α) were performed on paraffin-embedded sections. The total vascular inflammation score (TVIS), angiogenesis score (AS), and numbers of VEGF-expressing and TNF-α-expressing cells were analyzed in the fascia and muscle.

Results

Significant fasciitis was detected in most of the patients DM with or without myositis-specific/associated antibodies, while mild fasciitis was detected in four patients with PM, two of whom were positive for anti-aminoacyl-tRNA synthetase (anti-ARS) antibodies. The AS and the number of VEGF-expressing cells in the fascia of patients with DM were significantly greater than those of patients with PM; no significant difference was observed in muscle in patients with DM and PM. The number of VEGF-expressing cells in the fascia correlated with the AS of DM patients. In early-phase DM, the AS, the number of VEGF-expressing cells, and the TVIS in the fascia were significantly higher than in muscle. However, no significant differences were observed in these scores excluding the TVIS between muscle and the fascia in late-phase DM. In DM patients, the TVIS correlated with the AS in the fascia, while the number of TNF-α-expressing cells correlated with the TVIS and the number of VEGF-expressing cells in the fascia.

Conclusion

Angiogenesis, the number of VEGF-expressing cells, and the degree of inflammation were higher in the fascia in DM than in PM, and were increased predominantly in the fascia rather than in the muscle in early-phase DM. The degree of inflammation correlated with that of angiogenesis in the fascia of DM. The fascia can therefore be a primary site of inflammation and angiogenesis in the pathogenesis of DM.

Myalgia in Patients with Dermatomyositis and Polymyositis Is Attributable to Fasciitis Rather Than Myositis: A Retrospective Study of 32 Patients who Underwent Histopathological Examinations

OBJECTIVE

To determine the association between fasciitis and the clinical variables in patients with dermatomyositis (DM) and polymyositis (PM).

METHODS

We retrospectively reviewed the medical records of 32 patients (24 DM, 8 PM) with newly diagnosed DM and PM and in whom fascia and muscle specimens were histopathologically examined. The relationship between fasciitis and the clinical variables was statistically analyzed. These included age, sex, myalgia, muscle weakness, creatine kinase (CK) and aldolase activities, anti-Jo1 antibody, interstitial lung disease, and malignancy.

RESULTS

Twenty (62.5%) of the 32 patients who underwent the histopathological examination of a fascia specimen had fasciitis, including 18 (75%) of 24 patients with DM and 2 (25%) of 8 patients with PM. The frequency of fasciitis was significantly higher among the patients with DM than among the patients with PM (p < 0.05). Histopathologically, fasciitis in PM was very mild in comparison to that in DM. The frequency of myalgia in patients with fasciitis was significantly higher than that in patients without fasciitis (p < 0.05). However, myalgia was not associated with myositis. There were no significant differences in the patients with and without fasciitis in age, sex, manual muscle test 8 scores, CK or aldolase activities, or the presence of anti-Jo1 antibodies and malignancy.

CONCLUSION

The frequency of fasciitis was significantly higher among patients with DM than among those with PM. Fasciitis, rather than myositis, was associated with myalgia.

Comparative analyses of muscle MRI and muscular function in anti-synthetase syndrome patients and matched controls: a cross-sectional study

BACKGROUND

Magnetic resonance imaging (MRI) of thigh muscles is increasingly used to assess disease activity and damage extent in chronic myositis, but the validity of the findings is not clear. Here, the primary aim was to compare thigh MRI findings in patients having chronic myositis associated with anti-synthetase syndrome (ASS) and in matched healthy controls.

METHODS

Cross-sectional analyses of thigh muscle MRI, muscular function and creatinine kinase (CK) were performed in 68 ASS patients (median disease duration 71 months) and 67 controls matched for age and gender. MRI changes associated with disease activity (edema in muscles and fascia) and damage (fatty replacement and muscle volume reduction) were assessed semiquantitatively, giving a total MRI score of 0-78 (total edema 0-42 and total damage 0-36).

RESULTS

ASS patients had higher total MRI score than the matched controls (14.1 versus 3.0; p < 0.001) and less muscle strength (p < 0.001). Muscle edema was more frequent in ASS patients than controls (38% versus 12%), as was fatty replacement (42% versus 4%). In ASS patients, we found that the total edema score correlated with CK, but 23% of the patients with normal CK had score > 18. Muscle compartment analyses in ASS patients showed that muscle edema was most pronounced anteriorly, while fatty replacement dominated posteriorly.

CONCLUSIONS

This study showed, for the first time, the magnitude of difference in muscle MRI findings between chronic myositis cases and matched controls. In ASS patients, muscle MRI appeared to provide useful complementary information to muscle strength and CK levels in the assessment of myositis.

Thigh muscle MRI in immune-mediated necrotising myopathy: extensive oedema, early muscle damage and role of anti-SRP autoantibodies as a marker of severity

OBJECTIVES

The aims of this study were to define the pattern of muscle involvement in patients with immune-mediated necrotising myopathy (IMNM) relative to those with other inflammatory myopathies and to compare patients with IMNM with different autoantibodies.

METHODS

All Johns Hopkins Myositis Longitudinal Cohort subjects with a thigh MRI (tMRI) who fulfilled criteria for IMNM, dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM) or clinically amyopathic DM (CADM) were included in the study. Muscles were assessed for intramuscular and fascial oedema, atrophy and fatty replacement. Disease subgroups were compared using univariate and multivariate analyses. Patients with IMNM with anti-signal recognition particle (SRP) autoantibodies were compared with those with IMNM with anti-HMG-CoA reductase (HMGCR) autoantibodies.

RESULTS

The study included 666 subjects (101 IMNM, 176 PM, 219 DM, 17 CADM and 153 IBM). Compared with DM or PM, IMNM was characterised by a higher proportion of thigh muscles with oedema, atrophy and fatty replacement (p<0.01). Patients with IMNM with anti-SRP had more atrophy (19%, p=0.003) and fatty replacement (18%, p=0.04) than those with anti-HMGCR. In IMNM, muscle abnormalities were especially common in the lateral rotator and gluteal groups. Fascial involvement was most widespread in DM. Fatty replacement of muscle tissue began early during the course of disease in IMNM and the other groups. An optimal combination of tMRI features had only a 55% positive predictive value for diagnosing IMNM.

CONCLUSIONS

Compared with patients with DM or PM, IMNM is characterised by more widespread muscle involvement. Anti-SRP-positive patients have more severe muscle involvement than anti-HMGCR-positive patients.

Thigh magnetic resonance imaging for the evaluation of disease activity in patients with idiopathic inflammatory myopathies followed in a single center

INTRODUCTION

In patients with idiopathic inflammatory myopathies (IIM), magnetic resonance imaging (MRI) has been proposed as a useful tool for diagnosis and follow-up. It may identify muscle inflammation (edema) and fatty infiltration for evaluation of disease activity and damage. Little information is available on the role of MRI in assessment of large cohorts of adult patients with IIM.

METHODS

Fifty-one patients underwent MRI of the thigh muscles, laboratory tests, and clinical evaluation, including Physician Global Assessment (PGA) of myositis activity and the Manual Muscle Test 8 (MMT8).

RESULTS

Muscle edema correlated significantly with creatine kinase values (P = 0.017) and PGA (P < 0.001). A significant correlation between edema and MMT8 values (P = 0.025) was observed when patients with muscle fatty infiltration were excluded. With respect to clinical diagnosis, the sensitivity of MRI was 92.3%, and specificity was 83.3%.

CONCLUSIONS

MRI appears to provide additional information that complements clinical and biochemical examinations. Muscle Nerve 54: 666-672, 2016.

Subscapular bursitis as a rare manifestation of dermatomyositis: a case report

Dermatomyositis (DM) is characterized by proximal muscle weakness and characteristic skin rash. Pain is a less common feature and usually indicates inflammation of extramuscular structures such as fascia. Here we report a rare case of subscapular bursitis in a 48-year-old woman with DM. She initially presented with severe, sharp, stabbing pain in her right shoulder that worsened with shoulder movement. Magnetic resonance imaging (MRI) revealed inflammation in the right subscapular bursae. A few months later, the patient developed periungual erythema, Gottron's papules, and shawl sign with muscle pain in her thighs. DM was diagnosed based on the presence of interface dermatitis on skin biopsy and diffuse muscle inflammation on MRI. Bursitis and myalgia responded incompletely to nonsteroidal anti-inflammatory drugs but promptly to corticosteroids. Here we report a case of subscapular bursitis as a rare manifestation of DM. Pain in patients with DM may warrant physicians to evaluate for the presence of additional inflammatory processes in the perimuscular structures.

Classification, diagnosis, and management of idiopathic inflammatory myopathies

The detection and characterization of a large array of autoantibodies, including at least 8 different antisynthetase, anti-SRP, -200/100 (HMGCR), -Mi-2, -CADM-140 (MDA5), -SAE, -p155, -MJ (NXP-2), and -PMS1, frequently associated with distinct and well-defined clinicopathological features, allowed for significant improvement in the definition and diagnosis of idiopathic inflammatory myopathies (IIM). Classification remains difficult, with lingering divergence between the different specialties involved in IIM care, but several categories clearly stand out, including dermatomyositis (DM), overlap myositis (OM), polymyositis, necrotizing myositis, and sporadic inclusion body myositis (s-IBM). Biopsy and histological analysis remain crucial, particularly in the absence of autoantibodies, to accurately specify the diagnosis and rule out mimics such as muscular dystrophies and metabolic myopathies. Numerous infectious agents (in particular human immunodeficiency virus and human T cell lymphotrophic virus-1) and drugs (statins, tumor necrosis factor inhibitors, and proton pump inhibitors) can cause mimic IIM that must also be excluded. Pharmacological treatment, in addition to glucocorticoids and immunoglobulins, now includes mycophenolate mofetil and rituximab, which proved helpful in resistant cases, particularly rituximab in DM and OM. Exercise, initially seen as potentially deleterious, recently was shown to be efficacious and safe. IIM can thus be reasonably well controlled in most cases, although aggressive disease remains refractory to treatment, including some cases of necrotizing myopathy. Sporadic IBM still seems resistant to all medications tested to date.

Magnetic resonance imaging of inflammatory myopathies

The following article reviews the role of magnetic resonance imaging (MRI) in patients with idiopathic inflammatory myopathies (IIMs), focusing on the 3 major types of IIM: polymyositis, dermatomyositis, and inclusion-body myositis. After a brief introduction with general information about IIM, we will discuss the reasons why MRI plays an important role in the diagnosis and management of patients with polymyositis, dermatomyositis, and inclusion-body myositis. Magnetic resonance imaging can confirm the diagnosis and can help to phenotype the disease. Moreover, the support of MRI is important in addressing the muscle biopsy site and in reducing the high false-negative rate of biopsy when performed in a blind fashion. In monitoring therapy, MRI can add important information about the activity of the muscle disease and can identify cases where continued immunosuppressive therapy is no longer warranted owing to complete fatty replacement of the muscles. Lastly, we provide an overview about some advanced MRI techniques that focus more on function than on morphology of muscle.