Objective: We have tried to clarify the clinical importance of the measurement of serum type-I interferon (IFN) in patients with anti-melanoma differentiation-associated gene 5 Ab (MDA5 Ab)-positive dermatomyositis (DM).
Methods: We studied 30 patients with DM: 10 were anti-MDA5 Ab-positive and 20 were anti-MDA5 Ab-negative. At each patient's initial visit, serum IFN-α, IFN-β, interleukin 18 (IL-18), ferritin, and the titer of anti-MDA5 Ab were measured using enzyme-linked immunosorbent assays (ELISAs). The associations between the IFNs and with the other variables were examined.
Results: Rapidly progressive interstitial lung disease (RPILD) was confirmed in 10 patients, most of whom were complicated in the anti-MDA5 Ab-positive DM patients. The presence of clinically amyopathic dermatomyositis (CADM) as well as the serum concentrations of IFN-α and ferritin was significantly higher in the anti-MDA5 Ab-positive DM patients. Serum concentration of IL-18 did not differ between anti-MDA5 Ab-positive and anti-MDA5 Ab-negative groups; however, a positive correlation was found between IFN-α and IL-18 in the anti-MDA5 Ab-positive DM patients (r = 0.8139, p = 0.0146).
Conclusion: Serum IFN-α can be used as a useful biomarker in patients with anti-MDA5 Ab-positive DM, which may reflect the presence of RPILD.
Keywords: CADM; Ferritin; IFN-α; RPILD; anti-MDA5 antibody.