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Abstract
Objective To identify the characteristic pathologic features of dermatomyositis (DM) associated with anti-Mi-2 autoantibodies (anti-Mi-2 DM).
Methods We reviewed 188 muscle biopsies from patients (1) pathologically diagnosed with DM through the sarcoplasmic expression for the myxovirus-resistant protein A and (2) serologically positive for 1 of 5 DM-specific autoantibodies (DMSAs) (anti-Mi-2, n = 30; other DMSAs, n = 152) or negative for all 5 DMSAs (n = 6). We then compared the histopathologic and immunohistochemical features of patients with anti-Mi-2 DM to those with non-Mi-2 DM and patients with anti-synthetase syndrome (ASS) (n = 212) using the t test, Fisher exact test, and a logistic regression model.
Results Patients with anti-Mi-2 DM showed significantly higher severity scores in muscle fiber and inflammatory domains than non-Mi-2 DM patients. The presence of perifascicular necrosis, increased perimysial alkaline phosphatase activity, and sarcolemmal membrane attack complex deposition was more frequent in patients with anti-Mi-2 DM (p < 0.01). After Bonferroni correction, there were no significant differences in the percentages of the features mentioned above between the patients with anti-Mi-2 DM and those with ASS (p > 0.01).
Conclusion Perifascicular necrosis and perimysial pathology, features previously reported in ASS, are common in patients with anti-Mi-2 DM. Our findings not only assist in differentiating anti-Mi-2 DM from other DM subtypes but also suggest the possibility of an overlapping mechanism between anti-Mi-2 DM and ASS.
Classification of Evidence This study provides Class II evidence that the muscle biopsies of DM patients with anti-Mi-2 autoantibodies are more likely to demonstrate higher severity scores in muscle fiber and inflammatory domains.
Glossary
- ACP=
- acid phosphatase;
- ALP=
- alkaline phosphatase;
- ARS=
- aminoacyl-transfer RNA synthetase;
- ASS=
- anti-synthetase syndrome;
- CK=
- creatine kinase;
- COX=
- cytochrome C oxidase;
- DM=
- dermatomyositis;
- DMSA=
- DM-specific autoantibody;
- ENMC-DM=
- European Neuromuscular Centre DM workshop;
- H&E=
- hematoxylin & eosin;
- IFN1=
- type I interferon;
- ILD=
- interstitial lung disease;
- IMPP=
- immune myopathies with perimysial pathology;
- MAC=
- membrane attack complex;
- MDA5=
- melanoma differentiation-associated gene 5;
- mGT=
- modified Gomori trichrome;
- MHC=
- major histocompatibility complex;
- MHCn=
- neonatal myosin heavy chain;
- MxA=
- myxovirus resistance protein A;
- NXP-2=
- nuclear matrix protein 2;
- PFA=
- perifascicular atrophy;
- PFN=
- perifascicular necrosis;
- PM-ALP=
- perimysial connective tissue ALP activity;
- PM-Fr=
- perimysial connective tissue fragmentation;
- SAE=
- small ubiquitin-like modifier activating enzyme;
- TIF1-γ=
- transcription intermediary factor 1-γ
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
See the Highlighted Changes supplement, showing the changes made in this updated version: links.lww.com/WNL/C488.
Class of Evidence: NPub.org/coe
- Received February 4, 2020.
- Accepted in final form September 4, 2020.
- © 2020 American Academy of Neurology
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