Epidemiology
In England and Wales, the overall rate of people presenting with pneumothorax (in both primary and secondary care combined) is 24/100,000 a year for men and approximately 10/100,000 a year for women.[5] Hospital admission rates are estimated at 16.7/100,000 years for men and 5.8/100,000 years for women.[5]
Spontaneous pneumothorax has an incidence of 17-24 and 1-6 per 100,000 population per annum for men and women, respectively.[5][6] Smoking increases the likelihood of spontaneous pneumothorax by 22 times for men and by 9 times for women, compared with not smoking. The incidence is directly related to the amount smoked.[7]
Risk factors
The peak age for primary spontaneous pneumothorax is 20 years at the first episode. Primary spontaneous pneumothoraces rarely occur after 40 years of age.[22]
Invasive procedures such as transcutaneous needle aspiration of lung lesions, thoracentesis, endoscopic transbronchial biopsy, central venous catheter placement, and positive pressure ventilation are associated with iatrogenic pneumothoraces.
The air trapping associated with airway inflammation during an asthmatic attack can cause rupture of alveolar sacs leading to the development of a pneumothorax.
This is the leading cause of secondary spontaneous pneumothoraces and is due to rupture of subpleural emphysematous blebs.[27]
Secondary spontaneous pneumothoraces occur in 1.5% of cases of active pulmonary tuberculosis. Ruptures of subpleural tuberculous cysts are thought to be responsible.[28]
Secondary spontaneous pneumothorax is a frequent occurrence in cystic fibrosis and is associated with more severe disease. About 16% to 20% of patients with cystic fibrosis >18 years of age will experience a pneumothorax at some time in their lives. Recurrent contralateral pneumothoraces occur in 40% of patients.[29][30]
A multi-system disease of women, characterised by cystic lung destruction that can result in recurrent pneumothoraces.[31]
An autosomal dominant inheritable disease characterised by pulmonary cysts, spontaneous pneumothoraces, benign skin lesions, and renal cancers. Mutations in the gene that encodes for folliculin have been identified in individuals with this familial spontaneous pneumothorax.[36]
This is a smoking-related interstitial lung disease, characterised by the development of cystic changes in the lung that predisposes to pneumothorax.[37]
A rare disease characterised by disseminated non-Langerhans cell histiocytosis involving multiple organs. Pulmonary involvement is uncommon but the lung can become infiltrated by lipid-laden histiocytes, resulting in diffuse interstitial cystic changes and pneumothorax.[38]
There are reports of families afflicted with Marfan syndrome whose members suffered multiple bilateral episodes of primary spontaneous pneumothoraces. In this population, primary spontaneous pneumothoraces are attributed to pulmonary tissue fragility related to defective fibrillin.[32]
There have been a few case reports of primary spontaneous pneumothoraces in patients with homocystinuria. The pathophysiology of this association is unknown.[33]
Pneumothorax can occur in bronchogenic carcinomas and in a variety of cancers that have metastasised to the lungs. The pneumothoraces can develop following chemotherapy. It is postulated that necrosis of the peripherally located cancer causes the tumour to rupture into the pleural space, resulting in a pneumothorax.[34][35]
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