Musculoskeletal Ultrasound in Inclusion Body Myositis: A Comparative Study with Magnetic Resonance Imaging

272nd ENMC international workshop: 10 Years of progress - revision of the ENMC 2013 diagnostic criteria for inclusion body myositis and clinical trial readiness. 16-18 June 2023, Hoofddorp, The Netherlands

Since the publication of the 2013 European Neuromuscular Center (ENMC) diagnostic criteria for Inclusion Body Myositis (IBM), several advances have been made regarding IBM epidemiology, pathogenesis, diagnostic tools, and clinical trial readiness. Novel diagnostic tools include muscle imaging techniques such as MRI and ultrasound, and serological testing for cytosolic 5'-nucleotidase-1A antibodies. The 272nd ENMC workshop aimed to develop new diagnostic criteria, discuss clinical outcome measures and clinical trial readiness. The workshop started with patient representatives highlighting several understudied symptoms and the urge for a timely diagnosis. This was followed by presentations from IBM experts highlighting the new developments in the field. This report is composed of two parts, the first part providing new diagnostic criteria on which consensus was achieved. The second part focuses on the use of outcome measures in clinical practice and clinical trials, highlighting current limitations and outlining the goals for future studies.

Relationship Between Hand Function and Handheld Ultrasound Imaging in Inclusion Body Myositis

OBJECTIVE

Ultrasound studies in inclusion body myositis (IBM) have reported a characteristic pattern of increased echointensity in the flexor digitorum profundus (FDP) with relative sparing of the flexor carpi ulnaris (FCU). We examined the relationship between echointensity of the FDP and FCU muscles and hand strength or patient-reported outcomes (PROs).

METHODS

A total of 15 patients with IBM were recruited. Ultrasound images of the FDP and FCU muscles were obtained by a point-of-care ultrasound and graded using the modified Heckmatt score. Hand grip and neutral pinch strength were measured by dynamometry. PROs were assessed by the IBM Upper Extremity Function Scale.

RESULTS

FDP and/or FCU modified Heckmatt score showed a significant relationship with grip, neutral pinch strength, and PROs.

CONCLUSIONS

Point-of-care ultrasound examination of the forearm may serve as an extension of the neuromuscular examination. The semi-qualitative echointensity rating based on modified Heckmatt score seems to correlate well with the objective strength measurement and PROs.

Could ultrasound and muscle elastography be associated with clinical assessment, laboratory and nailfold capillaroscopy in juvenile dermatomyositis patients?

BACKGROUND

Juvenile Dermatomyositis (JDM) is the most common idiopathic inflammatory myopathy in children. Imaging exams are useful for muscle assessment, with ultrasonography (US) being a promising tool in detecting disease activity and tissue damage. There are few studies about muscle elastography.

OBJECTIVES

Our aim was to associate clinical, laboratory, and nailfold capillaroscopy (NC) assessments with US in JDM patients; and to compare the findings of US and Strain Elastography (SE) from patients and healthy controls.

METHODS

An analytic cross-sectional study was performed with JDM patients and healthy controls. Patients underwent clinical exam to access muscle strength and completed questionnaires about global assessment of the disease and functional capacity. Patients were submitted to NC and measurement of muscle enzymes. All subjects underwent US assessment, using gray scale, Power Doppler (PD), and SE.

RESULTS

Twenty-two JDM patients and fourteen controls, aged between 5 and 21 years, matched for age and sex were assessed. In qualitative and semi-quantitative gray scale, we observed a higher frequency of alterations in patients (p < 0.001), while in PD, there was a higher frequency of positivity in patients' deltoids and anterior tibialis (p < 0.001). Active disease was associated with an important change in the semi-quantitative gray scale in deltoids (p = 0.007), biceps brachii (p = 0.001) and quadriceps femoris (p = 0.005). The SE demonstrated a high negative predictive value of 87.2.

CONCLUSION

US was able, through gray scale, to differentiate JDM patients from controls, while PD achieved such differentiation only for deltoids and anterior tibialis. The semi-quantitative gray scale showed disease activity in proximal muscles. SE was not able to differentiate patients from controls.

Imaging With PET/CT of Diffuse CD8 T-Cell Infiltration of Skeletal Muscle in Patients With Inclusion Body Myositis

BACKGROUND AND OBJECTIVES

Inclusion body myositis (IBM) is a progressive autoimmune skeletal muscle disease in which cytotoxic CD8+ T cells infiltrate muscle and destroy myofibers. IBM has required a muscle biopsy for diagnosis. Here, we administered to patients with IBM a novel investigational PET tracer 89Zr-Df-crefmirlimab for in vivo imaging of whole body skeletal muscle CD8 T cells. This technology has not previously been applied to patients with autoimmune disease.

METHODS

Four patients with IBM received 89Zr-Df-crefmirlimab followed by PET/CT imaging 24 hours later, and the results were compared with similar imaging of age-matched patients with cancer. Mean standardized uptake value (SUVmean) was measured for reference tissues using spherical regions of interest (ROIs).

RESULTS

89Zr-Df-crefmirlimab was safe and well-tolerated. PET imaging demonstrated diffusely increased uptake qualitatively and quantitatively in IBM limb musculature. Quantitation of 89Zr-Df-crefmirlimab intensity in ROIs demonstrated particularly increased CD8 T-cell infiltration in patients with IBM compared with patients with cancer in quadriceps (SUVmean 0.55 vs 0.20, p < 0.0001), biceps brachii (0.62 vs 0.26, p < 0.0001), triceps (0.61 vs 0.25, p = 0.0005), and forearm finger flexors (0.71 vs 0.23, p = 0.008).

DISCUSSION

89Zr-Df-crefmirlimab uptake in muscles of patients with IBM was present at an intensity greater than the comparator population. The ability to visualize whole body in vivo cytotoxic T-cell tissue infiltration in the autoimmune disease IBM may hold utility as a biomarker for diagnosis, disease activity, and therapeutic development and potentially be applicable to other diseases with cytotoxic T-cell autoimmunity.

Inclusion Body Myositis

PURPOSE OF REVIEW

This article highlights the clinical and diagnostic features of inclusion body myositis (IBM) and provides recent insights into the pathomechanisms and therapeutic strategies of the disease.

RECENT FINDINGS

IBM is an often-misdiagnosed myopathy subtype. Due to the insidious onset and slow progression of muscle weakness, it can often be dismissed as a sign of aging as it commonly presents in older adults. While challenging to recognize upon initial clinical evaluation, the recent recognition of specialized stains highlighting features seen on muscle pathology, the use of diagnostic tools such as the anti-cytosolic 5'-nucleotidase 1A antibody biomarker, and the ability of muscle imaging to detect patterns of preferential muscle involvement seen in IBM has allowed for earlier diagnosis of the disease than was previously possible. While the pathogenesis of IBM has historically been poorly understood, several ongoing studies point toward mechanisms of autophagy and highly differentiated cytotoxic T cells that are postulated to be pathogenic in IBM.

SUMMARY

Overall advancements in our understanding of IBM have resulted in improvements in the management of the disease and are the foundation of several strategies for current and upcoming novel therapeutic drug trials in IBM.

Inclusion body myositis: evolving concepts

PURPOSE OF REVIEW

To discuss recent developments in our understanding of epidemiology, diagnostics, biomarkers, pathology, pathogenesis, outcome measures, and therapeutics in inclusion body myositis (IBM).

RECENT FINDINGS

Recent epidemiology data confirms a relatively higher prevalence in the population aged above 50 years and the reduced life expectancy. Association with cancer and other systemic disorders is better defined. The role of magnetic resonance imaging (MRI) and ultrasound in diagnosis as well as in following disease progression has been elucidated. There are new blood and imaging biomarkers that show tremendous promise for diagnosis and as outcome measures in therapeutic trials. Improved understanding of the pathogenesis of the disease will lead to better therapeutic interventions, but also highlights the importance to have sensitive and responsive outcome measures that accurately quantitate change.

SUMMARY

There are exciting new developments in our understanding of IBM which should lead to improved management and therapeutic options.

Inflammatory myopathies: an update for neurologists

Idiopathic inflammatory myopathies (IIM) are a heterogenous group of treatable myopathies. Patients present mainly to the rheumatologist and neurologists, complaining of acute or subacute onset of proximal weakness. Extramuscular manifestations may occur, including involvement of the lungs, skin, and joints. Classically, the diagnosis used to be made based on the creatine kinase level increase, abnormalities in electroneuromyography and presence of inflammatory infiltrates in the muscle biopsy. Recently, the importance of autoantibodies has increased, and now they may be identified in more than half of IIM patients. The continuous clinicoseropathological improvement in IIM knowledge has changed the way we see these patients and how we classify them. In the past, only polymyositis, dermatomyositis and inclusion body myopathy were described. Currently, immune-mediated necrotizing myopathy, overlap myositis and antisynthetase syndrome have been considered the most common forms of IIM in clinical practice, increasing the spectrum of classification. Patients previously considered to have polymyositis, in fact have these other forms of seropositive IIM. In this article, we reviewed the new concepts of classification, a practical way to make the diagnosis and how to plan the treatment of patients suffering from IIM.

The Emerging Era of Interventional Imaging in Rheumatology: An Overview During the Coronavirus Disease-2019 (COVID-19) Pandemic

Imaging has long been taking its place in the diagnosis, monitor, and prognosis of rheumatic diseases. It plays a vital role in the appraisal of treatment. Key progress in the clinical practice of rheumatology is the innovation of advanced imaging modalities; such as musculoskeletal ultrasound (MSUS), computerized tomography (CT) and magnetic resonance imaging (MRI). These modalities introduced a promising noninvasive method for visualizing bone and soft tissues to enable an improved diagnosis. The use of MSUS in rheumatology is considered a landmark in the evolution of the specialty and its ease of use and many applications in rheumatic diseases make it a forerunner instrument in the practice. The use of MSUS among rheumatologists must parallel the development rate of the excellence revealed in the specialty. Moreover, innovative interventional imaging in rheumatology (III-R) is gaining fame and key roles in the near future for a comprehensive management of rheumatic diseases with precision. This review article throws light on the emergence of these robust innovations that may reshape the guidelines and practice in rheumatology, in particular, efforts to enhance best practice during the coronavirus disease 2019 (COVID-19) pandemic are endorsed.

Bildgebung der Muskulatur bei Neuromuskulären Erkrankungen – von der Initialdiagnostik bis zur Verlaufsbeurteilung

Die bildgebende Diagnostik hat sich zu einem integralen Element der Betreuung von PatientInnen mit neuromuskulären Erkrankungen entwickelt. Als wesentliches Diagnostikum ist hierbei die Magnetresonanztomografie als breit verfügbares und vergleichsweise standardisiertes Untersuchungsverfahren etabliert, wobei die Sonografie der Muskulatur bei hinreichend erfahrenem Untersucher ebenfalls geeignet ist, wertvolle diagnostische Informationen zu liefern. Das CT hingegen spielt eine untergeordnete Rolle und sollte nur bei Kontraindikationen für eine MRT in Erwägung gezogen werden. Zunächst wurde die Bildgebung bei Muskelerkrankungen primär in der Initialdiagnostik unter vielfältigen Fragestellungen eingesetzt. Das Aufkommen innovativer Therapiekonzepte bei verschiedenen neuromuskulären Erkrankungen machen neben einer möglichst frühzeitigen Diagnosestellung insbesondere auch eine multimodale Verlaufsbeurteilung zur Evaluation des Therapieansprechens notwendig. Auch hier wird die Bildgebung der Muskulatur als objektiver Parameter des Therapieerfolges intensiv diskutiert und in Forschung wie Praxis zunehmend verwendet.

Muscle Sonography in Inclusion Body Myositis: A Systematic Review and Meta-Analysis of 944 Measurements

Inclusion body myositis (IBM) is a slowly progressive muscle weakness of distal and proximal muscles, which is diagnosed by clinical and histopathological criteria. Imaging biomarkers are inconsistently used and do not follow international standardized criteria. We conducted a systematic review and meta-analysis to investigate the diagnostic value of muscle ultrasound (US) in IBM compared to healthy controls. A systematic search of PubMed/MEDLINE, Scopus and Web of Science was performed. Articles reporting the use of muscle ultrasound in IBM, and published in peer-reviewed journals until 11 September 2021, were included in our study. Seven studies were included, with a total of 108 IBM and 171 healthy controls. Echogenicity between IBM and healthy controls, which was assessed by three studies, demonstrated a significant mean difference in the flexor digitorum profundus (FDP) muscle, which had a grey scale value (GSV) of 36.55 (95% CI, 28.65–44.45, p < 0.001), and in the gastrocnemius (GC), which had a GSV of 27.90 (95% CI 16.32–39.48, p < 0.001). Muscle thickness in the FDP showed no significant difference between the groups. The pooled sensitivity and specificity of US in the differentiation between IBM and the controls were 82% and 98%, respectively, and the area under the curve was 0.612. IBM is a rare disease, which is reflected in the low numbers of patients included in each of the studies and thus there was high heterogeneity in the results. Nevertheless, the selected studies conclusively demonstrated significant differences in echogenicity of the FDP and GC in IBM, compared to controls. Further high-quality studies, using standardized operating procedures, are needed to implement muscle ultrasound in the diagnostic criteria.

Polymyositis: does it really exist as a distinct clinical subset?

PURPOSE OF REVIEW

To summarize information on polymyositis; diagnosis, definitions, published data and opinions.

RECENT FINDINGS

Polymyositis originally referred to inflammatory muscle diseases presenting with muscle weakness and inflammatory cell infiltrates on muscle tissue visible by microscopy. Over time and with improved technology to immunophenotype infiltrating inflammatory cells and characterize muscle fibres, the meaning of polymyositis changed and became more specific. There is ongoing controversy over the term polymyositis, with proponents for a strict definition based on histopathological and immunohistochemical features on muscle biopsies whereas others advocate for a broader clinical and histopathological phenotype. Over the past decades, the discovery of several myositis-specific autoantibodies together with distinct histopathological features have enabled the identification of new subsets previously labelled as polymyositis notably the antisynthetase syndrome and the immune-mediated necrotizing myopathies thus reducing the number of patients classified as polymyositis.

SUMMARY

There are still a small number of patients among the idiopathic inflammatory myopathies that can be classified as polymyositis as discussed in this review but the entity is now considered relatively rare.