[Connective tissue disease-associated interstitial lung diseases : A pattern-based approach to diagnosis]

Connective tissue diseases (CTD) encompass a heterogeneous group of systemic immune-mediated disorders affecting connective tissue throughout the body. Pulmonary involvement is a common and clinically significant manifestation of CTD, with interstitial lung disease (ILD) representing a major contributor to both morbidity and mortality. Therefore, early detection of CTD-ILD is critical, and a multidisciplinary approach is paramount for both diagnosis and patient management. In this context, high-resolution computed tomography (HRCT) plays a pivotal role not only in recognizing characteristic ILD patterns but also in monitoring disease progression and guiding further management. Although the most frequent imaging pattern in CTD-ILD is nonspecific interstitial pneumonia (NSIP), the spectrum of pulmonary manifestations is complex and heterogeneous. Other patterns such as usual interstitial pneumonia (UIP), organizing pneumonia (OP), lymphocytic interstitial pneumonia (LIP), and diffuse alveolar damage (DAD) can also occur, showing distinct associations with specific CTD. Moreover, overlap and transition between patterns are not uncommon, further complicating the diagnostic process. This review aims to provide a comprehensive overview of the most relevant pulmonary manifestations of CTD, particularly ILD, with a focus on HRCT-based pattern recognition in order to enhance radiologist's familiarity with their spectrum of imaging appearances.