Pleuropulmonary involvement in ankylosing spondylitis.

Pleuropulmonary involvement was long described as an uncommon and late event in the course of ankylosing spondylitis (AS). This belief was based on studies that relied on symptoms and chest radiographs to evaluate the lungs. However, pleuropulmonary involvement in AS patients is usually asymptomatic, and the early lesions are undetectable on chest radiographs. Apical fibrosis, interstitial infiltrates, and pleural thickening were considered to be the main patterns. However, the introduction of high-resolution computed tomography (HRCT) has led to the description of many pulmonary abnormalities that are clinically silent and undetectable on plain radiographs. These abnormalities mainly affect the interstitium and have no influence on respiratory function, which is dependent on the severity of chest wall inflammation or ankylosis in recent-onset and established AS, respectively. Cytological and histological studies suggest that, in common with uveitis and aortic regurgitation, the structural lung changes shown by HRCT may be specific of AS.