Clinical significance of serum levels of anti‐transcriptional intermediary factor 1‐γ antibody in patients with dermatomyositis

Abstract Dermatomyositis (DM) is an autoimmune inflammatory disease characterized by skin eruptions and myositis. Anti‐transcriptional intermediary factor 1‐γ antibody (anti‐TIF1‐γ Ab) is one of the most frequently detected myositis‐specific autoantibodies and adults positive for anti‐TIF1‐γ have markedly higher rates of malignancy. Our aim was to determine the clinical associations of anti‐TIF1‐γ levels in 31 Japanese adult DM patients positive for anti‐TIF1‐γ. We determined associations between the anti‐TIF1‐γ index and patient characteristics and disease severities. Sixteen patients with anti‐TIF1‐γ Ab had concomitant malignancies. A mild positive correlation was found between the levels of serum creatine phosphokinase at the first visit and anti‐TIF1‐γ levels. In contrast, there was no significant difference in the anti‐TIF1‐γ Ab index between patients with and without malignancy. Dysphagia tended to be observed in patients with malignancy. On sequential analysis, anti‐TIF1‐γ levels in patients without malignancy were lower or turned negative after treatment for DM. Ab titers tended to be sustained in patients with stage IV malignancies. Interestingly, a re‐increase in the Ab titer was observed on recurrence of malignancy or increase in DM activity. Four patients were completely cured of their malignancies, and anti‐TIF1‐γ levels in three patients turned negative with the loss of DM activity. These data suggest that higher anti‐TIF1‐γ titers may not directly indicate the presence of malignancy. Nevertheless, longitudinal changes in the anti‐TIF1‐γ index in individual patients may partially reflect activities of both DM and malignancy.