Bronchiectasis: the permanent enlargement of the airways
Bronchiectasis is a disease in which there is the permanent enlargement of parts of the airways of the lung. Symptoms typically include a chronic cough with mucus production. Other symptoms include shortness of breath, coughing up blood, and chest pain. Wheezing and nail clubbing may also occur. Those with the disease often get frequent lung infections. This article will be focusing on Epidemiology, aetiology, pathophysiology, clinical features, and complications of bronchiectasis.
Periods of worsening may occur due to infection. In these cases, antibiotics are recommended. Common antibiotics used include amoxicillin, erythromycin, or doxycycline. Antibiotics, such as erythromycin, may also be used to prevent the worsening of the disease. Airway clearance techniques, a type of physical therapy, are also recommended. Medications to dilate the airways and inhaled steroids may be used during sudden worsening, but there are no studies to determine effectiveness. There are also no studies on the use of inhaled steroids in children. Surgery, while commonly done, has not been well studied. Lung transplantation may be an option in those with very severe diseases.
The disease affects between 1 per 1000 and 1 per 250,000 adults. The disease is more common in women and increases as people age. It became less common since the 1950s with the introduction of antibiotics. It is more common among certain ethnic groups such as indigenous people.
Epidemiology
The disease affects between 1 per 1000 and 1 per 250,000 adults. The disease is more common in women and increases as people age. It became less common since the 1950s, with the introduction of antibiotics. It is more common among certain ethnic groups such as indigenous people.
An estimated 350,000 to 500,000 adults have bronchiectasis in the United States. The disease is more common in women and elderly individuals over the age of 65.
Aetiology
Many causes can induce or contribute to the development of bronchiectasis. The frequency of these different causes varies with geographic location. Cystic fibrosis is identified as a cause in up to half of cases.
Bronchiectasis without CF is known as non-CF bronchiectasis. Historically, about half of all cases of non-CF bronchiectasis were found to be idiopathic, or without a known cause. However, more recent studies with a more thorough diagnostic workup have found an aetiology in 60 to 90% of patients.
Cystic fibrosis
It is a genetic disorder that affects the lungs, but also
the pancreas, liver, kidneys, and intestine. It is caused by mutations in the
CFTR protein, a chloride channel expressed in epithelial cells. Lung disease
results from clogging of the airways due to mucus build-up decreased
mucociliary clearance, and resulting inflammation. In later stages, changes to
the structure of the lung, such as bronchiectasis, occur. Around 5 to 10% of
all patients with cystic fibrosis develop bronchiectasis.
Airway Obstruction
Airway obstruction can be caused by either an intraluminal mass such as a tumour or a foreign body. The presence of an airway obstruction leads to a cycle of inflammation. It is important to identify the presence of obstruction because surgical resection is often curative if an obstruction is a cause. In adults, foreign body aspiration is often associated with an altered state of consciousness. The foreign body is often unchewed food or part of a tooth or crown. Bronchiectasis that results from foreign body aspiration generally occurs in the right lung in the lower lobe or posterior segments of the upper lobe.
Lung infections
A range of bacterial, mycobacterial, and viral lung infections are associated with the development of bronchiectasis. Bacterial infections commonly associated with bronchiectasis include P. aeruginosa, H. influenzae, and S. pneumoniae. Gram-negative bacteria are more commonly implicated than gram-positive bacteria. A history of mycobacterial infections such as tuberculosis can lead to damage of the airways that predisposes to bacterial colonization. Severe viral infections in childhood can also lead to bronchiectasis through a similar mechanism. Nontuberculous mycobacteria infections such as Mycobacterium avium complex are found to be a cause in some patients. Recent studies have also shown Nocardia infections to been implicated in bronchiectasis.
Aspergillosis
Allergic bronchopulmonary aspergillosis (ABPA) is an inflammatory disease caused by hypersensitivity to the fungus Aspergillus fumigatus. It is suspected in patients with a long history of asthma and symptoms of bronchiectasis such as a productive, mucopurulent cough. Imaging often shows peripheral and central airway bronchiectasis, which is unusual in patients with bronchiectasis caused by other disorders.
Autoimmune diseases
Several autoimmune diseases have been associated with bronchiectasis. Specifically, individuals with rheumatoid arthritis and Sjögren syndrome have increased rates of bronchiectasis. In these diseases, the symptoms of bronchiectasis usually present later in the disease course. Other autoimmune diseases such as ulcerative colitis and Crohn’s disease also have an association with bronchiectasis. Additionally, graft-versus-host disease in patients who have undergone stem cell transplantation can lead to bronchiectasis as well.
Lung injury
Bronchiectasis could be caused by: inhalation of ammonia and other toxic gases, chronic pulmonary aspiration of stomach acid from oesophageal reflux, or a hiatal hernia.
Congenital
Bronchiectasis may result from congenital disorders that affect cilia motility or ion transport. A common genetic cause is a cystic fibrosis, which affects chloride ion transport. Another genetic cause is primary ciliary dyskinesia, a rare disorder that leads to immotility of cilia and can lead to situs inversus. When situs inversus is accompanied by chronic sinusitis and bronchiectasis, this is known as Kartagener’s syndrome. Other rare genetic causes include Young’s syndrome and Williams-Campbell syndrome. Tracheobronchomegaly or Mourner-Kuhn syndrome is a rare condition characterized by significant tracheobronchial dilation and recurrent lower respiratory tract infections. Individuals with alpha 1-antitrypsin deficiency are particularly susceptible to bronchiectasis, due to the loss of inhibition to enzyme elastase which cleaves elastin. This decreases the ability of the alveoli to return to normal shape during expiration.
Ciggarette smoking
A causal role of tobacco smoke in bronchiectasis has not been demonstrated. Nonetheless, tobacco smoking can worsen pulmonary function and accelerate the progression of disease that is already present.
Pathophysiology
The development of bronchiectasis requires two factors: an infectious insult and impaired drainage, obstruction, or a defect in host defence. This triggers a host immune response from neutrophils (elastases), reactive oxygen species, and inflammatory cytokines that result in progressive destruction of normal lung architecture. In particular, the elastic fibres of bronchi are affected. The result is permanent abnormal dilation and destruction of the major bronchi and bronchiole walls.
The “vicious cycle” theory is the generally accepted explanation for the pathogenesis of bronchiectasis. In this model, a predisposed individual develops an excessive inflammatory response to pulmonary infection or tissue injury. The inflammation that results is partially responsible for the structural damage to the airways. The structural abnormalities allow for the stasis of mucus, which favours continued chronic infection and the persistence of the vicious cycle.
Endobronchial tuberculosis commonly leads to bronchiectasis, either from bronchial stenosis or secondary traction from fibrosis. Traction bronchiectasis characteristically affects peripheral bronchi (which lack cartilage support) in areas of end-stage fibrosis.
Clinical features
Commonly include a cough productive of frequent green or yellow sputum lasting months to years. Other common symptoms include difficulty breathing, wheezing (a whistling sound when breathing), and chest pain. Bronchiectasis may also present with coughing up blood in the absence of sputum, which has been called “dry bronchiectasis.”
People often report frequent bouts of “bronchitis” requiring therapy with repeated courses of antibiotics. People with bronchiectasis may have bad breath from active infection. On examination, crepitations and expiratory rhonchi may be heard with auscultation. Nail clubbing is a rare symptom.
Complications
The complications of bronchiectasis include serious health conditions, such as respiratory failure and atelectasis. Respiratory failure occurs when not enough oxygen passes from the lungs into the blood. Atelectasis occurs when one or more segments of the lungs collapse or do not inflate properly. Other pulmonary complications include lung abscesses and empyema. Cardiovascular complications include cor pulmonale, in which there is enlargement and failure of the right side of the heart as a result of disease of the lungs.
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