[Respiratory manifestations of ankylosing spondylitis (50 cases)]

Fifty patients with ankylosing spondylitis underwent radiography of the chest. In addition, 2 of them had bronchography, 3 had computerized tomography (CT) of the chest, 9 had respiratory function tests and 8 head ventilation/perfusion study by the Xenon method. Seven thoracic images were questionably specific of spondylitis, showing plural symphysis, strips of atelectasis, pleural thickening, apical pulmonary sclerosis and opacities of the diaphragmatic hilum. CT proved valuable in 1 case to confirm pulmonary fibrosis and in 2 cases to reveal that pleural thickening was continuous with an opacity ensheathing the vertebral body. In 7 out of 9 cases the functional restrictive deficit was accompanied by normal or supranormal functional residual capacity and increased residual volume. In all patients explored by the Xenon method, there was apical-caudal inversion of the ventilation/perfusion ratio. These findings suggest 3 pathogenic hypotheses: mere sequelae of hypoventilation, specific lung tissue fibrosis, extension by continuity of the vertebra-ensheathing process to the subpleural spaces.