Nailfold videocapillaroscopy findings are associated with IIM subtypes and IFN activation

This study aimed to characterize nailfold videocapillaroscopy (NVC) features in patients with different subtypes of Idiopathic inflammatory myopathy (IIM) and to investigate the correlations between NVC findings, myositis-specific antibody (MSA) subtypes, disease activity, cytokine profiles, and interferon-stimulated gene (ISG) expression levels. This cross-sectional observational single-center study included 55 IIM patients, categorized into MDA5 (+), anti-aminoacyl-tRNA-synthetase antibodies (ARS) (+), and MSA(-) groups based on their MSA profiles. Demographic data, laboratory tests, and NVC assessments were systematically collected and analyzed. The relative expression of type I ISGs in whole blood, as well as serum cytokine and chemokine profiles, were measured. Statistical analyses were performed to explore correlations between NVC scores and clinical parameters, including serum biomarkers. NVC abnormalities were observed in most IIM patients, with significant differences in NVC features among the MSA subgroups. The MDA5(+) group exhibited significantly higher scores for capillary dilation (P < 0.01), giant capillaries (P < 0.05), microhemorrhages (P < 0.01), and abnormal capillary morphology (P < 0.05) compared to the ARS (+) group. ISG expression and cytokine levels were upregulated in IIM patients, with active disease patients showing significantly higher levels of certain ISGs and cytokines compared to clinically stable patients. Notably, specific NVC score dimensions were positively correlated with the levels of certain ISGs and cytokines. For example, microhemorrhage, capillary dilation, and capillary density all had significantly positive correlations with MX1, IFI27, IP-10, RANTES, and GROα (P < 0.05). And giant capillary is also related to levels of IFI27, SDF-1α, IP-10, RANTES, and GROα (P < 0.05). IIM patients exhibit distinct NVC abnormalities, which vary across different MSA subtypes. NVC findings have potential clinical value in screening disease activity and interferon pathway activation in IIM patients.