Inclusion body myositis: correlation of clinical outcomes with histopathology, electromyography and laboratory findings

Sporadic Inclusion Body Myositis at the Crossroads between Muscle Degeneration, Inflammation, and Aging

Sporadic inclusion body myositis (sIBM) is the most common muscle disease of older people and is clinically characterized by slowly progressive asymmetrical muscle weakness, predominantly affecting the quadriceps, deep finger flexors, and foot extensors. At present, there are no enduring treatments for this relentless disease that eventually leads to severe disability and wheelchair dependency. Although sIBM is considered a rare muscle disorder, its prevalence is certainly higher as the disease is often undiagnosed or misdiagnosed. The histopathological phenotype of sIBM muscle biopsy includes muscle fiber degeneration and endomysial lymphocytic infiltrates that mainly consist of cytotoxic CD8+ T cells surrounding nonnecrotic muscle fibers expressing MHCI. Muscle fiber degeneration is characterized by vacuolization and the accumulation of congophilic misfolded multi-protein aggregates, mainly in their non-vacuolated cytoplasm. Many players have been identified in sIBM pathogenesis, including environmental factors, autoimmunity, abnormalities of protein transcription and processing, the accumulation of several toxic proteins, the impairment of autophagy and the ubiquitin-proteasome system, oxidative and nitrative stress, endoplasmic reticulum stress, myonuclear degeneration, and mitochondrial dysfunction. Aging has also been proposed as a contributor to the disease. However, the interplay between these processes and the primary event that leads to the coexistence of autoimmune and degenerative changes is still under debate. Here, we outline our current understanding of disease pathogenesis, focusing on degenerative mechanisms, and discuss the possible involvement of aging.

Exploring challenges in the management and treatment of inclusion body myositis

PURPOSE OF REVIEW

This review provides an overview of the management and treatment landscape of inclusion body myositis (IBM), while highlighting the current challenges and future directions.

RECENT FINDINGS

IBM is a slowly progressive myopathy that predominantly affects patients over the age of 40, leading to increased morbidity and mortality. Unfortunately, a definitive cure for IBM remains elusive. Various clinical trials targeting inflammatory and some of the noninflammatory pathways have failed. The search for effective disease-modifying treatments faces numerous hurdles including variability in presentation, diagnostic challenges, poor understanding of pathogenesis, scarcity of disease models, a lack of validated outcome measures, and challenges related to clinical trial design. Close monitoring of swallowing and respiratory function, adapting an exercise routine, and addressing mobility issues are the mainstay of management at this time.

SUMMARY

Addressing the obstacles encountered by patients with IBM and the medical community presents a multitude of challenges. Effectively surmounting these hurdles requires embracing cutting-edge research strategies aimed at enhancing the management and treatment of IBM, while elevating the quality of life for those affected.

Diagnosing and managing dysphagia in inclusion body myositis: a systematic review

OBJECTIVES

Dysphagia is a common debilitating clinical feature of IBM. However, the impact of dysphagia in IBM has been historically overlooked. This study aimed to identify, evaluate and summarize the evidence regarding the assessment and management of dysphagia in persons with IBM undergoing treatment.

METHODS

A systematic review was conducted using a multiengine search following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. Eligible studies had to employ an intervention for persons with IBM, report a swallowing outcome and be published in English. Quality assessments of the eligible studies were performed.

RESULTS

Of 239 studies found, 19 met the inclusion criteria. One study was rated as 'fair' and the rest as 'poor' quality, particularly due to the lack of published and validated swallowing assessment procedures and outcome measures. Cricopharyngeal (CP) dysfunction (12/19) was the most commonly reported swallowing abnormality. Interventions for disease management included pharmacological agents (10/19), followed by surgical (3/19), behavioral (1/19) and combined approaches (5/19). Interventions with immunosuppressants, botulinum toxin injection, balloon dilation and/or CP myotomy led to mixed and transient benefits. Few studies examining statins or behavioral therapies (primarily focused on respiratory function) showed no effects for dysphagia.

CONCLUSION

Various interventions have been reported to temporarily improve dysphagia in persons with IBM. However, these findings are based on limited and overall low-quality evidence. This study cautions against the generalization of these findings and emphasizes the need for further systematic research to improve the diagnosis and management of dysphagia in IBM.

Anti-Cytosolic 5'-Nucleotidase 1A in the Diagnosis of Patients with Suspected Idiopathic Inflammatory Myopathies: An Italian Real-Life, Single-Centre Retrospective Study

BACKGROUND

Anti-cytosolic 5'-nucleotidase 1A (anti-cN1A) antibodies were proposed as a biomarker for the diagnosis of inclusion body myositis (IBM), but conflicting specificity and sensitivity evidence limits its use. Our study aimed to assess the diagnostic accuracy of anti-cN1A in a cohort of patients who underwent a myositis line immunoassay for suspected idiopathic inflammatory myopathies (IIM). We also assessed the agreement between two testing procedures: line immunoassay (LIA) and enzyme-linked immunoassay (ELISA).

MATERIALS AND METHODS

We collected retrospective clinical and serological data for 340 patients who underwent a myositis antibody assay using LIA (EUROLINE Autoimmune Inflammatory Myopathies 16 Ag et cN-1A (IgG) line immunoassay) and verification with an anti-cN1A antibody assay using ELISA (IgG) (Euroimmun Lubeck, Germany).

RESULTS

The serum samples of 20 (5.88%) patients (15 females, 5 males, mean age 58.76 ± 18.31) tested positive for anti-cN1A using LIA, but only two out of twenty were diagnosed with IBM. Seventeen out of twenty tested positive for anti-cN1A using ELISA (median IQR, 2.9 (1.9-4.18)).

CONCLUSIONS

Our study suggests excellent concordance between LIA and ELISA for detecting anti-cN1A antibodies. LIA may be a rapid and useful adjunct, and it could even replace ELISA for cN1A assay. However, the high prevalence of diseases other than IBM in our cohort of anti-cN1A-positive patients did not allow us to consider anti-cN1A antibodies as a specific biomarker for IBM.

Atypical presentations of inclusion body myositis: Clinical characteristics and long-term outcomes

INTRODUCTIONS/AIMS

Inclusion body myositis (IBM) typically presents with progressive weakness preferentially involving finger flexors and quadriceps. Atypical presentations have been less commonly reported. Here, we aim to describe the clinical characteristics and long-term outcomes of IBM patients with atypical presentations.

METHODS

We retrospectively searched the Mayo Clinic medical records to identify IBM patients with atypical disease onset, seen between 2015 and 2020.

RESULTS

We identified 357 IBM patients, of whom 50 (14%) had an atypical presentation. Thirty-eight patients were diagnosed with IBM because they fulfilled one of the European Neuromuscular Center diagnostic categories at a later stage, 10 had all IBM histopathological features, and 2 were diagnosed on the basis of clinical and laboratory data. The most common presentation was dysphagia (50%), followed by asymptomatic hyperCKemia (24%; CK, creatine kinase), then foot drop (12%). 6% of patients presented with proximal arm weakness, 4% with axial weakness and 4% with facial diplegia. Median time from symptom onset to diagnosis was 9 y. Median age at diagnosis was 70.5 y. 16% of patients needed a walking aid. When tested, 86.5% of patients had impaired swallowing and 56% had elevated cytosolic nucleotidase-1A antibodies. Only 1/26 patients who received immunotherapy had minimal improvement. Upon follow-up, most patients had generalization of their weakness with a decline in their strength summated score of 0.082/mo.

DISCUSSION

A significant proportion of IBM patients may have an atypical presentation. Recognition of such heterogeneity could improve early diagnosis, prevent unnecessary immunotherapy, and provide insight for future diagnostic criteria development and clinical trials.

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.

Inclusion body myositis: Update on the diagnostic and therapeutic landscape

Inclusion body myositis (IBM) is a progressive muscle disease affecting patients over the age of 40, with distinctive clinical and histopathological features. The typical clinical phenotype is characterized by prominent involvement of deep finger flexors and quadriceps muscles. Less common presentations include isolated dysphagia, asymptomatic hyper-CKemia, and axial or limb weakness beyond the typical pattern. IBM is associated with marked morbidity as majority of patients eventually become wheelchair dependent with limited use of their hands and marked dysphagia. Furthermore, IBM mildly affects longevity with aspiration pneumonia and respiratory complications being the most common cause of death. On muscle biopsy, IBM is characterized by a peculiar combination of endomysial inflammation, rimmed vacuoles, and protein aggregation. These histopathological features are reflective of the complexity of underlying disease mechanisms. No pharmacological treatment is yet available for IBM. Monitoring for swallowing and respiratory complications, exercise, and addressing mobility issues are the mainstay of management. Further research is needed to better understand disease pathogenesis and identify novel therapeutic targets.