Category Causes Autoimmune disease Rheumatoid arthritis Sjögren syndrome Impaired host defenses Cystic fibrosis Primary ciliary dyskinesia Primary immunodeficiency HIV/AIDS Job's syndrome Post-infective Bacterial pneumonia Mycobacterium infection Viral infection Congenital Tracheobronchomegaly Marfan syndrome Williams–Campbell syndrome Young's syndrome Alpha-1 antitrypsin deficiency Hypersensitivity Allergic bronchopulmonary aspergillosis Inflammatory bowel disease Ulcerative colitis Crohn's disease Malignancy Chronic lymphocytic leukemia Graft-versus-host disease Obstruction Tumor Foreign body aspiration Lymphadenopathy Other Pneumonia Chronic aspiration Ammonia inhalation Smoke inhalation Radiation-induced lung disease Yellow nail syndrome There are many causes that can induce or contribute to the development of<unk> . The frequency of these different causes varies with geographic location. Cystic fibrosis is identified as a cause in up to half of cases.<unk>  without CF is known as non-CF<unk> . Historically, about half of all case of non-CF<unk>  were found to be idiopathic, or without a known cause. However, more recent studies with a more thorough diagnostic work-up have found an etiology in 60 to 90% of patients. Cystic fibrosis Cystic fibrosis is the most common life-threatening autosomal recessive disease in the United States and Europe. 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<unk> , occur. Around 5 to 10% of all patients with cystic fibrosis develop<unk> . Airway obstruction An airway obstruction can be caused by either an intraluminal mass such as a tumor or a foreign body. The presence of an airway obstruction leads to a cycle of inflammation. It is important to identify the presence of an obstruction because surgical resection is often curative if obstruction is the 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.<unk>  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<unk> . Bacterial infections commonly associated with<unk>  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<unk>  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<unk> . Impaired host defenses Impairments in host defenses that lead to<unk>  may be congenital, such as with primary ciliary dyskinesia, or acquired, such as with the prolonged use of immunosuppressive drugs. Additionally, these impairments may be localized to the lungs, or systemic throughout the body. In these states of immunodeficiency, there is a weakened or absent immune system response to severe infections that repeatedly affect the lung and eventually result in bronchial wall injury. HIV/AIDS is an example of an acquired immunodeficiency that can lead to the development of<unk> . 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<unk>  such as a productive, mucopurulent cough. Imaging often shows peripheral and central airway<unk> , which is unusual in patients with<unk>  caused by other disorders. Autoimmune diseases Several autoimmune diseases have been associated with<unk> . Specifically, individuals with rheumatoid arthritis and Sjögren syndrome have increased rates of<unk> . In these diseases, the symptoms of<unk>  usually presents later in the disease course. Other autoimmune diseases such as ulcerative colitis and Crohn's disease also have an association with<unk> . Additionally, graft-versus-host disease in patients who have undergone stem cell transplantation can lead to<unk>  as well. Lung injury<unk>  could be caused by: inhalation of ammonia and other toxic gases, chronic pulmonary aspiration of stomach acid from esophageal reflux, or a hiatal hernia. Congenital<unk>  may result from congenital disorders that affect cilia motility or ion transport. A common genetic cause is 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<unk> , this is known as Kartagener's syndrome. Other rare genetic causes include Young's syndrome and Williams-Campbell syndrome. Tracheobronchomegaly, or Mournier-Kuhn syndrome is a rare condition characterized by significant tracheobronchial dilation and recurrent lower respiratory tract infections. Individuals with alpha 1-antitrypsin deficiency have been found to be particularly susceptible to<unk> , 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. Cigarette smoking A causal role for tobacco smoke in<unk>  has not been demonstrated. Nonetheless, tobacco smoking can worsen pulmonary function and accelerate the progression of disease that is already present.
Bronchiectasis
Chronic obstructive pulmonary disease
Plastic bronchitis
Tracheobronchomalacia
Bronchitis kettle
Asbestosis
Acute bronchitis
Dust pneumonia