Do bullae and emphysema increase risk of pneumothorax in silicosis?

This study was carried out using questionnaire items on occupational history and conventional computed tomography of lungs. Differences between two groups (silicosis with and without secondary spontaneous pneumothorax) in terms of age, interval of exposure-diagnosis and therefore silica exposure duration were assessed by independent t-test. Fisher's exact test was used to determine the association between secondary spontaneous pneumothorax and both emphysema and bullae.We found a significant association between secondary spontaneous pneumothorax and bullae in acute and accelerated silicosis.Pneumothorax in silicosis could be attributed to previous bullae.Pneumothorax is the presence of air in the pleural cavity [1]. The spontaneous form is generally due to the rupture of subpleural blebs. Clinical diagnosis of pneumothorax is established by history, physical examination and where possible, by radiological investigations [2-4]. Secondary spontaneous pneumothorax (SSP) occurs as a complication of an underlying lung disease, which can be identified. Chronic obstructive pulmonary disease (COPD) and Pneumocystis carinii pneumonia are the most common conditions associated with SSP [1,5]. Pleural involvement in silicosis is rare and SSP is the only recognised pleural complication of silicosis [6-11]. SSP is usually unilateral, when it occurs in the course of silicosis. There are only a few reports in which patients with silicosis had bilateral SSP [9,11]. Some investigators have reported that emphysema and bullae formation may lead to the occurrence of SSP [3,12]. Emphysema is defined as enlargement of airspaces distal to the terminal bronchiole, accompanied by destructive changes of alveolar walls [13]. It is usually classified into the following three main subtypes: centrilobular emphysema; panlobular emphysema; and paraseptal emphysema [14]. Bullae can develop in association with any type of emphysema. A bulla is a sharply demarcated area with a diameter greater than 1