- • Bronchiectasis is characterized by chronic
cough productive of purulent sputum.
- • Chest radiography demonstrates abnormally dilated
airways and mucous plugging, characterized by “ring” shadows, “gloved
finger” shadows, or air-filled cystic spaces that may include
- • Spirometry reveals a pattern of airflow obstruction.
- • Cystic fibrosis is one of the most common causes
of bronchiectasis. The classic CF phenotype includes chronic sinopulmonary
disease, pancreatic exocrine insufficiency, and abnormal sweat chloride
Bronchiectasis is a pathological description of abnormally dilated,
distorted thick-walled medium-sized bronchi that are chronically
inflamed and infected by bacteria. The essential clinical feature
is chronic production of purulent sputum. Bronchiectasis is not
a single disease, but a pathological entity now recognized to be
associated with many different conditions. The process occurs in
airways that have sustained inflammatory injury with subsequent
loss of structural integrity of muscle, elastic tissue, and bronchial
cartilage. These abnormal dilated airways are susceptible to bacterial
colonization, which leads to neutrophil influx. Proteolytic neutrophil products
further damage lung tissue and disrupt ciliary function, and this
continued bronchial wall damage predisposes to further colonization
Cystic fibrosis (CF) is the most common inherited disorder among
whites in the United States, affecting one in 3200. One in 25 is
a carrier of the disease. The disease is caused by mutations in
a single gene, called the cystic fibrosis transmembrane conductance
regulator (CFTR), and is inherited in an autosomal recessive fashion.
Defective chloride transport across epithelial cells leads to dehydrated
secretions and exocrine gland dysfunction. Although multiple organs
are affected, the progression of bronchiectasis is the most common
cause of death and disability. Over 800 mutations in the gene that
encodes CFTR have been described, with the most common mutation, δF508,
seen in 66% of CF chromosomes.
Barker AF: Bronchiectasis. N Engl J Med 2002;346:1383.
(A recent review of bronchiectasis that provides
an excellent overview of the subject.)
Bronchiectasis is caused by a variety of insults to the airways.
A number of congenital and/or hereditary factors predispose
certain individuals to develop it, but bronchiectasis is not present
at birth. Primary or secondary infections are the most frequently
identified initiating factor in patients predisposed to bronchiectasis.
Other proinflammatory insults such as inhalation of toxins, aspiration
of gastric contents, abnormal immune responses (such as autoimmune
diseases), or environments exposures (tobacco smoke) can accelerate
the lung disease. Damage to the bronchial mucosa and accompanying
impairment of host defense eventually lead to chronic infection of
the airways regardless of the initial insult. A persistent inflammatory
response is established resulting in chronic sputum production and
perpetuation of airway injury. The most clearly defined mechanism
resulting in bronchiectasis is mutation of CFTR in CF.
CFTR functions as a cyclic adenosine monophosphate (cAMP)-regulated
chloride channel located in the apical membranes of epithelia affected
by CF. This defect leads to excess absorption of salt and water
at airway surfaces, dehydrating secretions ...