# Evaluating the Diagnostic Potential of Myxovirus Resistance Protein 1 (MX1) and Myxovirus Resistance Protein 2 (MX2) As Biomarkers in Idiopathic Inflammatory Myopathies

## TL;DR

This paper reviews how MX1 and MX2 proteins might help diagnose autoimmune muscle diseases like dermatomyositis by analyzing their presence in muscle tissue and blood.

## Contribution

The study systematically evaluates MX1 and MX2 as potential biomarkers for idiopathic inflammatory myopathies, focusing on their diagnostic accuracy and limitations.

## Key findings

- MX1 is consistently elevated in muscle tissue of IIM patients, especially in dermatomyositis, with high tissue specificity.
- MX2 is upregulated at the transcriptomic level, but lacks sufficient protein-level data and diagnostic clarity compared to MX1.
- Blood-based MX1 measurements are promising but prone to false positives due to factors like disease activity and treatment history.

## Abstract

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune muscle diseases characterized by proximal muscle weakness, systemic involvement, and high morbidity. Current diagnosis relies on clinical assessment, serology, and muscle biopsy, but challenges remain due to overlapping features and cases lacking clear biomarkers. Identifying molecular markers that reflect underlying disease pathways could improve diagnostic accuracy and patient stratification. This systematic review evaluates the diagnostic potential of myxovirus resistance protein 1 (MX1) and myxovirus resistance protein 2 (MX2), two interferon-inducible genes, as biomarkers in IIM and related conditions. A comprehensive literature search of PubMed, Embase, Web of Science, Ovid, and CINAHL (2015-2025) identified studies examining MX1 and/or MX2 in muscle disease. Eligible studies assessed diagnostic accuracy, sensitivity, specificity, or clinical relevance. Data extraction and risk of bias assessment followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Joanna Briggs Institute guidelines. Evidence suggests that MX1 is consistently elevated in affected muscle tissue in IIM, particularly dermatomyositis, where it demonstrates high tissue specificity, though its expression is not exclusive to this subtype. Peripheral or blood-based MX1 measurements show promise but risk false positives and are influenced by disease activity, prior treatment, and timing of sampling. MX2 is consistently upregulated at the transcriptomic level, but protein-level data are limited, and its incremental diagnostic value over MX1 remains unclear. Sensitivity and specificity vary across studies, emphasizing the need for standardized protocols and further benchmarking against other interferon-inducible biomarkers or clinical tools. Overall, MX1 is a valuable tissue biomarker for interferon-mediated myopathies, with potential applications in diagnosis, disease activity assessment, and monitoring systemic progression. Future prospective, multicenter, and longitudinal studies are required to validate these markers, address current limitations, and determine their utility in routine clinical practice.