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. 2023 Nov 20:16:5417-5426.
doi: 10.2147/JIR.S433239. eCollection 2023.

Sarcoplasmic Myxovirus Resistance Protein A: A Study of Expression in Idiopathic Inflammatory Myopathy

Jariya Waisayarat  1 , Phumin Wongsuwan  1 , Kiarttiyot Tuntiseranee  2 , Phu Waisayarat  3 , Charungthai Dejthevaporn  4 , Chaiyos Khongkhatithum  5 , Sirisucha Soponkanaporn  6
Affiliations

Sarcoplasmic Myxovirus Resistance Protein A: A Study of Expression in Idiopathic Inflammatory Myopathy

Jariya Waisayarat et al. J Inflamm Res. .

Abstract

Background: Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune diseases affecting primarily proximal muscles. Major subtypes include dermatomyositis, polymyositis, inclusion body myositis, immune-mediated necrotizing myopathy and antisynthetase syndrome. Overexpression of sarcoplasmic myxovirus-resistance protein A (MxA) has been observed in muscle biopsy specimens of dermatomyositis but is rarely seen in other subtypes of IIM and other myopathies.

Objective: We evaluate the expression of sarcoplasmic MxA and its diagnostic value in IIM and other myopathies.

Methods: One hundred and thirty-eight muscle biopsy specimens with the diagnosis of IIM and other myopathies from 2011 to 2020 were reviewed and stained for MxA by immunohistochemistry. The difference of the expression of MxA between IIM and other myopathies was analyzed by Fisher's exact test, and the sensitivity and specificity of MxA immunohistochemistry in the diagnosis of IIM were assessed.

Results: MxA protein was positive in 16/138 (11.6%) specimens. All 12 dermatomyositis specimens positive for MxA protein were positive in perifascicular area pattern. Only dermatomyositis specimens had a significantly higher percentage of positive sarcoplasmic MxA expression than specimens of other subtypes of IIM (p<0.001). Sarcoplasmic MxA expression for dermatomyositis diagnosis had a sensitivity of 46.15% (95% CI 26.59-66.63%) and a specificity of 94.44% (95% CI 81.34-99.32%) with the positive and negative likelihood ratio of 8.31 (95% CI 2.03-34.01) and 0.57 (95% CI 0.40-0.82), respectively.

Conclusion: The MxA immunohistochemistry is highly specific for dermatomyositis and should be added to a routine inflammatory panel of muscle biopsy. MxA expression should be cautiously interpreted to avoid pitfalls.

Keywords: dermatomyositis; idiopathic inflammatory myopathies; muscle biopsy; myxovirus resistance protein A.

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Conflict of interest statement

The authors report no conflicts of interest in this work.

Figures

Figure 1
Figure 1
(a) Study flow chart. (b) Patients categorization chart.
Figure 2
Figure 2
Representative immunohistochemical staining of MxA in muscle biopsies. Positive expression was defined by unequivocal sarcoplasmic staining in only intact fiber, not a regenerating or degenerated/necrotic fiber. (a) MxA negativity. (b) Moderate MxA positivity and perifascicular area pattern. (c) Strong MxA positivity and perifascicular area pattern (b and c in dermatomyositis patients). (d) Weak MxA positivity and non-perifascicular area pattern, positive fibers labeled with black arrow (in overlap myositis patient).
Figure 3
Figure 3
Necrotic fibers features on MxA and other IHCs. Sarcoplasmic MxA expression interpretation should be rigorous. (a) Five atrophic/shrinkage fibers with pale cytoplasmic stain were identified on H&E, 20X (black arrows). (b) The fibers revealed equivocal sarcoplasmic expression on MxA (black arrows). (c) The corresponding fibers revealed strong/clumping stained on MAC, 20X (black arrows). (d) Strong sarcoplasmic utrophin upregulation, 20X (black arrows). All stains represented that they were degenerated/necrotic fibers.
See this image and copyright information in PMC

References

    1. Plotz PH, Rider LG, Targoff IN, et al. Myositis: immunologic contributions to understanding cause, pathogenesis, and therapy. Ann Intern Med. 1995;122(9):715–724. doi: 10.7326/0003-4819-122-9-199505010-00010 - DOI - PubMed
    1. Dimachkie MM, Barohn RJ, Amato AA. Idiopathic inflammatory myopathies. Neurol Clin. 2014;32(3):595–628, vii. doi: 10.1016/j.ncl.2014.04.007 - DOI - PMC - PubMed
    1. Cox S, Limaye V, Hill C, et al. Idiopathic inflammatory myopathies: diagnostic criteria, classification and epidemiological features. Int J Rheum Dis. 2010;13(2):117–124. doi: 10.1111/j.1756-185X.2010.01472.x - DOI - PubMed
    1. Betteridge Z, McHugh N. Myositis-specific autoantibodies: an important tool to support diagnosis of myositis. J Intern Med. 2016;280(1):8–23. doi: 10.1111/joim.12451 - DOI - PubMed
    1. Mammen AL, Allenbach Y, Stenzel W, et al. 239th ENMC International Workshop: classification of dermatomyositis, Amsterdam, the Netherlands, 14-16 December 2018. Neuromuscul Disord. 2020;30(1):70–92. doi: 10.1016/j.nmd.2019.10.005 - DOI - PubMed