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Bronchiectasis is a disease that causes localized, irreversible dilation of part of the bronchial tree. It is classified as an obstructive lung disease, along with bronchitis and cystic fibrosis. Involved bronchi are dilated, inflamed, and easily collapsible, resulting in airflow obstruction and impaired clearance of secretions. Bronchiectasis is associated with a wide range of disorders, but it usually results from necrotizing bacterial infections, such as infections caused by the Staphylococcus or Klebsiella species or Bordetella pertussis.[1]
Rene Theophile Hyacinthe Laënnec, the man who invented the stethoscope, used his creation to first discover bronchiectasis in 1819.[2]. The disease was researched in greater detail by Sir William Osler in the late 1800s; in fact, it is suspected that Osler actually died of complications from undiagnosed bronchiectasis[3].
Dilation of the bronchial walls results in airflow obstruction and impaired clearance of secretions because the dilated areas disrupt normal air pressure in the bronchial tubes, causing sputum to pool inside the dilated areas instead of being pushed upward[4]. The pooled sputum provides an environment conducive to the growth of infectious pathogens, and these areas of the lungs are thus very vulnerable to infection. The more infections that the lungs experience, the more damaged the lung tissue and alveoli become. When this happens, the bronchial tubes become more inelastic and dilated, creating a self-perpetuating cycle of further damage to the lungs.
There are three types of brochiectasis, varying by level of severity. Fusiform (cylindrical) bronchiectasis (the most common type) refers to mildly inflamed bronchi that fail to taper distally. In varicose bronchiectasis, the bronchial walls appear beaded, because areas of dilation are mixed with areas of constriction. Saccular (cystic) bronchiectasis is characterized by severe and irreversible ballooning of the bronchi peripherally, with or without air-fluid levels.[5] Chronic productive cough is prominent, occurring in up to 90% of patients with bronchiectasis. Sputum is produced on a daily basis in 76% of patients.[6]
Generally, persons suffering from bronchiectasis tend to be infected by Haemophilus influenzae early on in the disease course. Secondary infection is usually due to Staphylococcus aureus; followed by Moraxella catarrhalis and finally Pseudomonas aeruginosa.[7]
There are both congenital and acquired causes of bronchiectasis. Kartagener syndrome, which affects the mobility of cilia in the lungs[8], aids in the development of the disease. Another common genetic cause is cystic fibrosis, in which a small number of patients develop severe localized bronchiectasis[9]. Young’s syndrome, which is clinically similar to cystic fibrosis, is thought to significantly contribute to the development of bronchiectasis. This is due to the occurrence of chronic, sinopulmonary infections.[10] Patients with alpha 1-antitrypsin deficiency have been found to be particularly susceptible to bronchiectasis, for unknown reasons. [11] Other less-common congenital causes include primary immunodeficiencies, due to the weakened or nonexistent immune system response to severe, recurrent infections that commonly affect the lung.[12]
Acquired bronchiectasis occurs more frequently, with one of the biggest causes being tuberculosis. Endobronchial tuberculosis commonly leads to bronchiectasis, either from bronchial stenosis or secondary traction from fibrosis.[13] An especially common cause of the disease in children is acquired immune deficiency syndrome, stemming from the human immunodeficiency virus. This disease predisposes patients to a variety of pulmonary ailments, such as pneumonia and other opportunistic infection.[14]. Bronchiectasis can sometimes be an unusual complication of inflammatory bowel disease, especially ulcerative colitis. It can occur in Crohn’s disease as well, but does so less frequently. Bronchiectasis in this situation usually stems from various allergic responses to inhaled fungus spores.[15] Recent evidence has shown an increased risk of bronchiectasis in patients with rheumatoid arthritis who smoke. One study stated a tenfold increased prevalence of the disease in this cohort[16]. Still, it is unclear as to whether or not cigarette smoke is a specific primary cause of bronchiectasis.
Other acquired causes of bronchiectasis involving environmental exposures include respiratory infections, obstructions, inhalation and aspiration of ammonia and other toxic gases, pulmonary aspiration, alcoholism, heroin (drug use), and various allergies.[17]
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