International consensus on a proposed score system for muscle biopsy evaluation in patients with juvenile dermatomyositis: A tool for potential use in clinical trials

Abstract

Objective. To devise and test a system with which to evaluate abnormalities on muscle biopsy samples obtained from children diagnosed with juvenile dermatomyositis (DM). Methods. We established an International Consensus Group on Juvenile DM Biopsy and carried out 2 phases of consensus process and scoring workshops. Biopsy sections (n ‫؍‬ 33) were stained by standard methods. The scoring tool was based on 4 domains of change: inflammatory, vascular, muscle fiber, and connective tissue. Using a Latin square design, biopsy samples were scored by 11 experts for items in each domain, and for a global abnormality measure using a 10-cm visual analog score (VAS 0 -10). The tool's reliability was assessed using an intraclass correlation coefficient (ICC) and scorer agreement (␣) by determining variation in scorers' ratings. Results. There was good agreement in many items of the tool, and several items refined between the meetings improved in reliability and/or agreement. The inflammatory and muscle fiber domains had the highest reliability and agreement. The overall VAS score for abnormality had high agreement and reliability, reaching an ICC of 0.863 at the second consensus meeting. Conclusion. We propose a provisional scoring system to measure abnormalities on muscle biopsy samples obtained from children with juvenile DM. This system needs to be validated, and then could be used in prospective studies to test which features of muscle pathology are prognostic of disease course or outcome. We suggest that the process we used could be a template for developing similar systems in other forms of myositis.

Extranodal lymphoid microstructures in inflamed muscle and disease severity of new‐onset juvenile dermatomyositis

“…In clinical practice, evaluation of muscle biopsy in the diagnosis of juvenile DM has become less common. Our histologic and molecular data, in conjunction with clinical data on muscle strength and vascular changes, underscore the importance of tissue histopathology in ascertaining juvenile DM prognosis (3,47). We report the unique observation that muscle lymphoid follicle-like organization is found among patients with more severe and difficult-to-treat disease, while those with milder disease have a scattering of inflammatory cells.…”

Anti-HMGCR Autoantibodies in Juvenile Idiopathic Inflammatory Myopathies Identify a Rare but Clinically Important Subset of Patients

“…Muscle biopsy. Where tissue was available for reassessment, muscle biopsies were processed, stained, and scored (using the International Juvenile Dermatomyositis score tool) by an expert pediatric neuropathologist (TSJ) blinded to clinical data 8,9 .…”

“…All biopsies had evidence of inflammation. Muscle biopsies were analyzed using the JDM muscle biopsy score tool as previously described by Wedderburn, et al 8,9 . …”

Efficacy of ultrasound elastography in detecting active myositis in children: can it replace MRI?

“…However the potential benefits of US elastography in children with active myositis have not been evaluated. Myositis affects the microvascular endothelium of muscle, resulting in swelling of vascular endothelium, obliteration of vessel lumena, perivascular inflammation, and degeneration of muscle fibers, all of which distort normal muscle architecture [18]. We postulated that the alteration in normal muscle architecture would lead to an alteration of muscle elasticity, which would be detectable by US elastography.…”