Spontaneous
Spontaneous pneumothoraces are divided into two types: ''primary'', which occurs in the absence of known lung disease, and ''secondary'', which occurs in someone with underlying lung disease. The exact cause of primary spontaneous pneumothorax is unknown however risk factors include male sex, smoking, and a family history of pneumothorax. The various suspected underlying mechanisms are discussed below.Secondary spontaneous pneumothorax occurs in the setting of a variety of lung diseases. The most common is chronic obstructive pulmonary disease which accounts for approximately 70% of cases. Known lung diseases that may increase the risk for pneumothorax are:
* Diseases of the airways: chronic obstructive pulmonary disease (especially when emphysema and lung bullae are present), acute severe asthma, cystic fibrosis
* Lung infections: pneumocystis pneumonia (PCP), tuberculosis, necrotizing pneumonia
* Interstitial lung diseases: sarcoidosis, idiopathic pulmonary fibrosis, histiocytosis X, lymphangioleiomyomatosis (LAM)
* Connective tissue diseases: rheumatoid arthritis, ankylosing spondylitis, polymyositis and dermatomyositis, systemic sclerosis, Marfan's syndrome and Ehlers-Danlos syndrome
* Cancer: lung cancer, sarcomas involving the lung
* Catamenial (occurring in relation to the menstrual cycle): endometriosis in the chest
In children, additional causes include measles, echinococcosis, inhalation of a foreign body, and particular congenital malformations (congenital cystic adenomatoid malformation and congenital lobar emphysema).
A rare genetic disorder, Birt-Hogg-Dubé syndrome, may cause spontaneous pneumothorax in families. It also causes skin lesions (fibrofolliculomas) and lung cysts, and carries an increased risk of kidney cancer. The lung cysts, which probably lead to increased risk of pneumothorax, tend to be in the lower lobes rather than the more common upper lobe cysts encountered in other conditions. Birt-Hogg-Dubé syndrome is caused by mutations in the ''FLCN'' gene (chromosome 17p11.2), which encodes a protein named folliculin. ''FLCN'' mutations and lung lesions have also been identified in familial cases of pneumothorax where other features of Birt-Hogg-Dubé syndrome are absent.
Traumatic
A traumatic pneumothorax may result from both blunt trauma and penetrating injuries to the chest wall. It may be observed in those exposed to an explosive blast, even if no direct injury to the chest has occurred. The most common mechanism is a cut to the pleura by a fractured rib.Medical procedures of the chest (iatrogenic), such as the taking of biopsy samples from lung tissue, inserting a central venous catheter into one of the chest veins, may lead to injury to the lung and resultant pneumothorax. The administration of positive pressure ventilation, either mechanical ventilation or non-invasive ventilation, may result in barotrauma (pressure-related injury) leading to a pneumothorax.
Adapted from the Wikipedia article Pneumothorax, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki
