[Interstitial lung disease associated with connective tissue disease]

Interstitial lung disease (ILD) is the most frequent organ manifestation in rheumatic autoimmune disease. Depending on the underlying autoimmune disease, differently pronounced affections of small airways, interstitial parenchyma, and vessels are found. The group of rheumatic autoimmune diseases mainly includes connective tissue diseases (CTDs), also known as collagen vascular diseases, such as rheumatoid arthritis (RA), systemic sclerosis, (SSc), systemic lupus erythematosus, primary Sjögren's syndrome, idiopathic inflammatory myositis (IIM), and interstitial pneumonia with autoimmune features (IPAF). Frequency and manifestations of parenchymal lung disorders are described clinically, radiologically, and morphologically in these entities. For the precise diagnosis and for the differentiation between the wide range of parenchymal disorders with known possible cause or with unknown origin, also called unclassifiable or idiopathic interstitial pneumonias (IIPs), high resolution computed tomography (HRCT) findings represent the diagnostic gold standard. A transbronchial biopsy, surgical biopsy, or cryobiopsy will be used in unclassifiable findings to confirm a definitive histological confirmation. A precise diagnosis of these ILDs is crucial since the different pathologies that encompass ILD have different therapeutic options. In this sense, the participation of a pneumologist, rheumatologist, radiologist, and pathologist become essential in the multidisciplinary evolution of ILD.