What are risk factors for primary spontaneous pneumothorax (PSP)?

Updated: Apr 28, 2020
  • Author: Brian J Daley, MD, MBA, FACS, FCCP, CNSC; Chief Editor: Mary C Mancini, MD, PhD, MMM  more...
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Answer

Risks factors for primary spontaneous pneumothorax (PSP) include the following:

  • Smoking
  • Tall, thin stature in a healthy person
  • Marfan syndrome
  • Pregnancy
  • Familial pneumothorax

Blebs and bullae (sometimes called referred to as ELCs) are related to the occurrence of primary spontaneous pneumothorax. Thoracic computed tomography (CT) scans of patients with PSP shows ipsilateral ELC in 89% and contralateral changes in 80% compared with a rate of 20% among control subjects matched for age and smoking. [2] Nonsmokers with PSP had CT scan ELC abnormalities of 80% compared with a rate of 0% among nonsmoker controls without PSP. [2]

Although patients with PSP do not have overt parenchymal disease, this condition is heavily associated with smoking—80-90% of PSP cases occur in smokers or former smokers, and the relative risk of PSP increases as the number of cigarettes smoked per day increases; that is, the risk of PSP is related to the intensity of smoking, with 102 times higher incidence rates in males who smoke heavily (ie, >22 cigarettes/day), compared with a sevenfold increase in males who smoke lightly (1-12 cigarettes/day). This incremental risk with increasing number of cigarettes smoked per day is much more pronounced in female smokers.

Typical PSP patients also tend to have a tall and thin body habitus. Whether height affects development of subpleural blebs or whether more negative apical pleural pressures cause preexisting blebs to rupture is unclear.

Pregnancy is an unrecognized risk factor, as suggested by a 10-year retrospective series in which five of 250 spontaneous pneumothorax cases were in pregnant women. [7] The cases were all managed successfully with simple aspiration or video-assisted thoracoscopic surgery (VATS), and no harm occurred to mother or fetus. [7]

Other associations with pneumothorax include increased intrathoracic pressure with the Valsalva maneuver, though contrary to popular belief, most spontaneous pneumothoraces occur while the patient is at rest. Changes in atmospheric pressure, proximity to loud music, and low-frequency noises are other reported factors.

Familial associations have been noted in more than 10% of patients. Some are due to rare connective tissue diseases, but mutations in the gene encoding folliculin (FLCN) have been described. These patients may represent an incomplete penetrance of an autosomal dominant genetic disorder. Birt-Hogg-Dube syndrome is characterized by benign skin growths, pulmonary cysts, and renal cancers and is caused by mutations in the FLCN gene.

In one family study, nine ascertained cases of spontaneous pneumothorax were reported among 54 members. A review of the literature summarized 61 reports of familial spontaneous pneumothorax among 22 families. Up to 10% patients with spontaneous pneumothorax report a positive family history. [8]

Although rare, spontaneous pneumothorax occurring bilaterally and progressing to tension pneumothorax has been documented.


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