Based on the antibody profiles of inflammatory myositis patients, we investigated the type 1 IFN (T1-IFN) signature in serum and DM skin to determine the relationship between T1-IFN and vasculopathy in anti-melanoma differentiation-associated 5 gene (MDA5) antibody-positive DM patients.

We examined 47 patients with new-onset inflammatory myositis. We divided them into three groups: the anti-MDA5 antibody-positive patients (MDA5 group, n = 16), the anti-aminoacyl-tRNA synthetase antibody-positive patients (aminoacyl-tRNA synthetase group, n = 12), and the double-negative patients (n = 19). Serum T1-IFN signatures were revealed by a functional reporter assay, and we evaluated the T1-IFN signatures of skin based on Mx1 expression by immunohistochemistry.

The numbers of patients with classical DM, clinically amyopathic DM and interstitial lung disease were 1, 15 and 13 in the MDA5 group, 2, 3 and 11 in the aminoacyl-tRNA synthetase group, and 10, 1 and 4 in the double-negative group, respectively. The signs of vasculopathies (i.e. palmer papules, skin ulcers and mononeuritis multiplex) were identified only in the MDA5 patients. Most of the MDA5 group showed the highest serum T1-IFN signatures among the three groups. In the histological analysis of DM skin, perivascular inflammations were significant in the MDA5 group. The MDA5 group’s Mx1 expression was significantly strong, distributed in blood vessels and interstitial fibroblasts, and had spread to deep dermis.

Anti-MDA5 antibody-positive DM patients showed high T1-IFN signatures in serum and affected skin. The high T1-IFN signatures of the MDA5 antibody-positive DM patients in serum and deep vasculatures suggested that T1-IFN may have important roles in the vasculopathy of these patients.