Spontaneous pneumothorax associated with ankylosing spondylitis.

OBJECTIVE To review the incidence and clinical characteristics of spontaneous pneumothorax in patients with ankylosing spondylitis (AS). METHODS This is a retrospective observational cohort study. Chest radiographs and medical records of patients with a diagnosis of AS from 1993 to 2003 in a tertiary referral centre were reviewed. RESULTS A total of 1028 patients with a diagnosis of AS were identified from July 1993 to July 2003. Twenty-two patients had typical apical lung fibrotic changes in the chest radiographs (22/1028, 2.1%). Three of these patients (3/22, 13.6%) with lung disease had pneumothorax. Two patients had recurrences and received video-assisted thoracoscopic surgery (VATS) on the second attack. The third patient received talc pleurodesis on the first attack and did not have a recurrence. The incidence of spontaneous pneumothorax in patients with AS was 0.29% (3/1028) with an incidence density of 64.85/100,000 patient-yr (95% confidence interval: 66.17-63.57/100,000). CONCLUSION Spontaneous pneumothorax appears to be exceedingly rare in AS unless there is an underlying fibrocystic lung disease, in which case its occurrence is not uncommon. Cigarette smoking may be an important co-factor. Once developed, recurrences are common even after treatment. Prophylactic procedures should thus be considered for the first attack of spontaneous pneumothorax.