Serum ferritin trajectories predict mortality risk in anti-melanoma differentiation-associated protein 5 antibody-positive dermatomyositis: a longitudinal cohort study

<title>Extract</title> Interstitial lung disease (ILD) associated with anti-melanoma differentiation-associated protein5 antibody positive (anti-MDA5+) dermatomyositis (DM) has a 6-month mortality rate of 33–66% despite aggressive immunosuppression, with rapidly progressive interstitial lung disease (RP-ILD) as the primary driver [1–4]. While elevated serum ferritin (SF) is an established prognostic biomarker in anti-MDA5+ DM, particularly among patients with RP-ILD, previous studies have relied on single-time-point measurements with inconsistent cutoffs due to heterogeneity [5–7], and comprehensive characterization of dynamic SF patterns during treatment in the real world is lacking. We hypothesized that SF trajectories could identify different subgroups with different mortality risks in patients with anti-MDA5+ DM.