The Correlation of Muscle Biopsy Scores with the Clinical Variables in Idiopathic Inflammatory Myopathies

Suparaporn Wangkaew1, *, Songkiet Suwansirikul2, Kantawut Aroonrungwichian1, Nuntana Kasitanon1, Worawit Louthrenoo1
1 Division of Rheumatology, Department of Internal Medicine, Chiang Mai University, Chiang Mai, Thailand
2 Department of Pathology, Chiang Mai University, Chiang Mai, Thailand

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© Wangkaew et al.; Licensee Bentham Open

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution-Non-Commercial 4.0 International Public License (CC BY-NC 4.0) (, which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Division of Rheumatology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand; Tel: +66-53-946449; Fax: +66-53-227203; E-mail:



To compare the muscle pathology findings among subgroups of idiopathic inflammatory myopathies (IIM) patients, and to determine the correlations of muscle biopsy scores with muscle power and creatine kinase (CK).


The medical records of IIM patients consisting of the demographic data, clinical parameters and laboratory conducted were retrospectively reviewed. Their initial muscle biopsies were reviewed, and four domains were scored: inflammation, vascular, muscle, and connective tissue.


Ninety-five IIM patients (28 patients with idiopathic polymyositis (PM) 9 idiopathic dermatomyositis (DM), 5 DM associated with malignancy, and 53 PM/DM associated with connective tissue disease) with median (IQR: Q1, Q3) disease duration of 1.2 (0.5, 3.1) months were included. No significant differences in initial muscle pathology findings and muscle pathology score among the subgroups were found. Muscle degeneration and endomysial fibrosis scores were negatively correlated with muscle power (r=-0.23 and-0.24, respectively, p<0.05) and positively correlated with CK (r=0.27 and 0.39, respectively, p<0.01). No significant correlation was detected either inflammation or vasculitis scores with muscle power and CK levels.


In this study, muscle biopsy cannot be used to differentiate among subgroups of IIM patients. In addition, we found only modest correlation of muscle biopsy scores with muscle power and CK. Further study is necessary to confirm our findings.

Keywords: Idiopathic inflammatory myopathies, IIM, Polymyositis, Dermatomyositis, Muscle biopsy, Biopsy score.