Anti-Ku antibody-positive interstitial lung disease: A retrospective study of 13 patients

Background Although anti-Ku antibodies have been reported in various connective tissue diseases (CTDs), data on the clinical characteristics of anti-Ku antibody-positive interstitial lung disease (ILD) remains limited. This study investigated the clinical, radiological, and pathological features of anti-Ku antibody-positive ILD. Methods We retrospectively reviewed 13 patients with anti-Ku antibody-positive ILD at our institution between 2018 and 2025. Data on baseline characteristics, imaging, pathology, treatment, and outcomes were collected. Results Seven patients were diagnosed with CTDs. CTD was present in idiopathic inflammatory myopathy (IIM; n = 2), Systemic sclerosis (SSc), IIM with SSc overlap, microscopic polyangiitis, rheumatoid arthritis, and Sjögren’s syndrome (n = 1, each). ILD preceded the diagnosis of CTDs in two of these patients. Nonspecific interstitial pneumonia (NSIP) was the most frequent pattern (n = 5, 38.5%) on chest computed tomography, followed by usual interstitial pneumonia (UIP, n = 4, 30.8%). On lung histopathology, NSIP with organizing pneumonia was the most frequent pathological pattern (n = 3, 37.5%), whereas UIP features were present in four patients. During the observation period (51.7 ± 32.1 months), four patients developed progressive pulmonary fibrosis (PPF). Among the seven patients in whom any radiological or pathological UIP feature was present, four (57.1%) developed PPF or experienced acute exacerbation. Conclusions Anti-Ku antibody-positive ILD can exhibit progressive fibrotic behavior regardless of the CTD diagnosis. Radiological and/or pathological UIP features might represent indicators of disease progression. Careful follow-up is encouraged to ensure the early detection of CTD and fibrotic progression.