Thoracic manifestations of the less common collagen diseases. A pictorial essay.

Systemic autoimmune diseases include different forms of vasculitides and collagen diseases. Among collagen diseases, the rarer entities include: Sjögren syndrome, dermatopolymyositis, ankylosing spondylitis, relapsing polychondritis and mixed connective tissue disorders. The diagnosis of these entities requires an integrated multidisciplinary approach. The radiological findings of collagen diseases are well known; however, the introduction of HRCT studies provides additional information and enable an early diagnosis. The more common thoracic manifestations of collagen diseases include interstitial pneumonia (usual, nonspecific and lymphocytic), bronchiolitis obliterans organizing pneumonia (BOOP), airway diseases (bronchiectasis, obliterative and constrictive bronchiolitis, follicular bronchiolitis), pleural abnormalities, diaphragmatic dysfunction, apical fibrosis. The aim of this pictorial essay is to present the main radiological and HRCT patterns related to the less common collagen diseases.