Respiratory infections

• Bacterial infections, such as those caused by Staphylococcus or Pseudomonas

• Mycobacterial infections, such as tuberculosis

• Viral infections caused by influenza, respiratory syncytial virus , adenoviruses, or SARS-CoV-2 (causes COVID-19)

Bronchial blockage

• Inhaled object

• Enlarged lymph nodes

• Lung tumor

• Lung surgery

• Mucus plugs (for example, due to allergic bronchopulmonary aspergillosis)

Inhalation injuries

• Injury from noxious fumes, gases, or particles

• Inhalation of stomach acid and food particles (for example, as a result of severe gastroesophageal reflux disease or a swallowing disorder)

Hereditary disorders

• Cystic fibrosis

• Primary ciliary dyskinesia, including Kartagener syndrome

• Alpha-1 antitrypsin deficiency

• Marfan syndrome

Immunologic abnormalities

• Immunoglobulin deficiency syndromes

• White blood cell dysfunction

• Complement deficiencies

• Certain autoimmune disorders, such as rheumatoid arthritis, Sjögren syndrome, and ulcerative colitis

Other conditions

• Human immunodeficiency virus (HIV) infection

• Diffuse panbronchiolitis (characterized by inflammation of the bronchioles throughout the lungs and chronic sinusitis)