Pulmonary involvement in ankylosing spondylitis

Two kinds of respiratory alterations can be found in patients with ankylosing spondylitis. The first consists in reduction of chest expansion due to the skeletal involvement. The second one is characterized by intrinsic lung disorders. Progressive stiffening of thoracic joints does not usually induce symptomatic dyspnea because of increased compensatory diaphragmatic function. As a consequence, vital capacity and total lung capacity are moderately reduced. Intrinsic lung damages consist in a fibro-bullous apical disease, described for the first time in the 1940s and now well recognized, and interstitial lung disease, recently found in studies using high-resolution computed tomography. Pulmonary cavities may be colonized by germs, especially mycetes.