Pneumothorax

Etiology and Epidemiology

A primary spontaneous pneumothorax occurs without trauma or underlying lung disease. Spontaneous pneumothorax with or without exertion occurs occasionally in teenagers and young adults, most frequently in males who are tall, thin, and thought to have subpleural blebs. Smoking and asthma are also risk factors for developing pneumothorax. Familial cases of spontaneous pneumothorax occur and have been associated with mutations in the folliculin gene (FCLN) . Over 150 unique FCLN mutations have been associated in the Birt-Hogg-Dube syndrome (skin fibrofolliculomas, multiple basal lung cysts, renal malignancies) or in patients with familial or recurrent spontaneous pneumothoraces. Individuals with other inherited disorders such as α ₁ -antitrypsin (see Chapter 421 ) and homocystinuria are also predisposed to pneumothorax. Patients with collagen synthesis defects such as Ehlers-Danlos disease (see Chapter 678 ) and Marfan syndrome (see Chapter 722 ) are at increased risk for the development of pneumothorax.

A pneumothorax arising as a complication of an underlying lung disorder but without trauma is a secondary spontaneous pneumothorax. Pneumothorax can occur in pneumonia, usually with empyema; it can also be secondary to pulmonary abscess, gangrene, infarct, rupture of a cyst or an emphysematous bleb (in asthma), or foreign bodies in the lung. In infants with staphylococcal pneumonia, the incidence of pneumothorax is relatively high. It can be found in children hospitalized with asthma exacerbations, and usually resolves without treatment. Pneumothorax is a serious complication in cystic fibrosis (see Chapter 432 ). Pneumothorax also occurs in patients with lymphoma or other malignancies, and in graft-versus-host disease with bronchiolitis obliterans.

External chest or abdominal blunt or penetrating trauma can tear a bronchus or abdominal viscus, with leakage of air into the pleural space. Ecstasy (methylenedioxymethamphetamine), crack cocaine, and marijuana abuse are associated with pneumothorax.

Iatrogenic pneumothorax can complicate transthoracic needle aspiration, tracheotomy, subclavian line placement, thoracentesis, or transbronchial biopsy. It may occur during mechanical or noninvasive ventilation, high-flow nasal cannula therapy, acupuncture, and other diagnostic or therapeutic procedures.

Catamenial pneumothorax, an unusual condition that is related to menses, is associated with diaphragmatic defects and pleural blebs.

Pneumothorax can be associated with a serous effusion (hydropneumothorax), a purulent effusion (pyopneumothorax), or blood (hemopneumothorax). Bilateral pneumothorax is rare after the neonatal period but has been reported after lung transplantation and with Mycoplasma pneumoniae infection and tuberculosis.