Serum interferon-λ3 as a short-term biomarker of disease control in anti-MDA5-positive dermatomyositis-associated ILD

This study aimed to assess the clinical utility of serum interferon-lambda 3 (IFN-λ3) as a sequential biomarker for treatment response and disease control in patients with anti-melanoma differentiation-associated gene 5 (MDA5) antibody-positive dermatomyositis (DM)-associated interstitial lung disease (ILD). Serum IFN-λ3 levels were measured in 24 patients with anti-MDA5 antibody-positive DM-ILD at diagnosis and 1 month after initiating immunosuppressive therapy. Patients were categorized into two groups based on clinical outcomes: a good control group (n = 16; survived without relapse for ≥ 1 year) and a poor control group (n = 8; died from ILD progression or relapse within 1 year). Changes in serum IFN-λ3 levels and differences between groups were analyzed. In the good control group, serum IFN-λ3 levels significantly decreased from 94.6 to 12.7 pg/mL (p < 0.001), whereas no significant change was observed in the poor control group (129.0 to 118.8 pg/mL). Furthermore, serum IFN-λ3 levels at 1 month were significantly lower in the good control group than in the poor control group (p = 0.004). Serum IFN-λ3 levels may reflect short-term treatment response and could serve as a useful sequential biomarker for assessing disease control in patients with anti-MDA5 antibody-positive DM-ILD.