Longitudinal changes in nailfold videocapillaroscopy findings differ by myositis-specific autoantibody in idiopathic inflammatory myopathy.

Objective: To assess the longitudinal changes in nailfold videocapillaroscopy (NVC) in patients expressing myositis-specific autoantibodies [anti-aminoacyl-tRNA synthetase (ARS), anti-transcriptional intermediary factor 1 (TIF1), and anti-melanoma differentiation-associated gene 5 (MDA5)].
Methods: This study was performed retrospectively, at a single site, on an observational cohort. Seventy-one idiopathic inflammatory myopathy patients were included (25 patients expressed anti-MDA5 Abs, 24 patients expressed anti-TIF1 Abs, and 22 patients expressed anti-ARS Abs). NVC findings included giant, enlarged, and reduced capillaries, haemorrhages, capillary ramification, disorganization of the vascular array, and capillary loss. NVC findings were compared from baseline to after disease activity stabilization.
Results: The frequency of enlarged capillaries at baseline was different among the three groups, and was significantly higher in patients with anti-TIF1 Abs compared with those with anti-ARS Abs (88% vs 55%, P < 0.05). Reduced capillaries were significantly increased in patients with anti-TIF1 Abs compared with those with anti-MDA5 (96% vs 44%, P < 0.0001) or anti-ARS Abs (96% vs 50%, P < 0.0005). Both enlarged and reduced capillaries improved after stabilization in patients with anti-MDA5 Abs (P < 0.0001 and P < 0.05, respectively). These improvements were not observed in patients expressing anti-TIF1 and anti-ARS Abs. However, a significant reduction in haemorrhages was observed in all three groups (P < 0.0001 for each group).
Conclusions: The results of this study demonstrate that longitudinal changes in NVC findings may vary depending on myositis-specific Ab expression. Therefore, it is crucial to assess individual NVC findings separately, as each finding may impact disease activity in a different manner.
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