Characteristics and outcomes of anti-Ku antibody–associated interstitial lung disease: a retrospective study of 60 patients

OBJECTIVE: Anti-Ku antibodies (Abs) are rare and detected in various autoimmune diseases (AIDs), presenting in various phenotypes, potentially affecting different organs including the lungs. This study aimed to describe the characteristics and evolution of interstitial lung disease (ILD) in anti-Ku-positive patients. METHODS: An observational, multicentre, retrospective study was conducted across 10 French University Hospitals between January 2010 and June 2025, including patients with anti-Ku Abs with ILD. Clinical data and all pulmonary function tests and chest CT scans available were reviewed for this study. ILD progression was defined using criteria inspired by the American Thoracic Society/European Respiratory Society/Japenese Respiratory Society/Asociación Latinoamericana de Tórax Clinical Practice Guidelines, applied across the entire follow-up period rather than within the 12-month timeframe, to capture all clinically meaningful progression events. To account for event timing, time to ILD progression was analysed as a time-to-event outcome using Cox proportional hazards models. RESULTS: Among 154 anti-Ku-positive patients (51 with idiopathic inflammatory myopathy, 46 with systemic lupus erythematosus, 30 with Sjögren's disease, 27 with systemic sclerosis), 60 (39%) had ILD (68% women, median age 56 years). The predominant ILD pattern was fibrotic non-specific interstitial pneumonia (27%, n=16). ILD was already present at AID diagnosis in 48 patients (80%). Forty-five (75%) patients progressed after a median time of 4 (2-11) years. Male sex (adjusted HR (aHR) 2.7; 95% CI 1.4 to 5.2) was associated with ILD progression. When the 12-month cut-off was strictly applied, only six patients fulfilled the progressive fibrosing ILD definition. Baseline pulmonary fibrosis was present in 34 (57%) patients and was associated with a reduced survival when adjusting for age at ILD diagnosis and cardiac involvement (aHR 6.5, 95% CI 1.5 to 28.2). CONCLUSION: ILD occurred in 39% of anti-Ku-positive patients and progressed in 75% of them, underscoring the importance of systematic ILD screening and monitoring in these patients.