Bacterial infections, such as those caused by Staphylococcus Staphylococcus aureus Infections Staphylococcus aureus is the most dangerous of all of the many common staphylococcal bacteria. These gram-positive, sphere-shaped (coccal) bacteria (see figure How Bacteria Shape Up) often cause... read more or Pseudomonas Pseudomonas Infections Any of several types of the gram-negative bacteria Pseudomonas, especially Pseudomonas aeruginosa, can infect different parts of the body, particularly in people who have serious medical problems... read more

Mycobacterial infections, such as tuberculosis Tuberculosis (TB) Tuberculosis is a chronic contagious infection caused by the airborne bacteria Mycobacterium tuberculosis. It usually affects the lungs. Tuberculosis is spread mainly when people breathe air... read more

Viral infections caused by influenza Influenza (Flu) Influenza (flu) is a viral infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general... read more , respiratory syncytial virus Respiratory Syncytial Virus (RSV) Infection and Human Metapneumovirus Infection Respiratory syncytial virus infection and human metapneumovirus infection cause upper and sometimes lower respiratory tract infections. Respiratory syncytial virus is a very common cause of... read more , or adenoviruses

Inhaled object

Enlarged lymph nodes

Lung tumor

Lung surgery

Mucus plugs (for example, due to allergic bronchopulmonary aspergillosis Allergic Bronchopulmonary Aspergillosis Allergic bronchopulmonary aspergillosis is an allergic lung reaction to a type of fungus (most commonly Aspergillus fumigatus) that occurs in some people with asthma or cystic fibrosis. People... read more )

Injury from noxious fumes, gases, or particles

Inhalation of stomach acid and food particles (for example, as a result of severe gastroesophageal reflux disease Gastroesophageal Reflux Disease (GERD) In gastroesophageal reflux disease, stomach contents, including acid and bile, flow backward from the stomach into the esophagus, causing inflammation in the esophagus and pain in the bottom... read more or a swallowing disorder)

Cystic fibrosis Cystic Fibrosis (CF) Cystic fibrosis is a hereditary disease that causes certain glands to produce abnormally thick secretions, resulting in tissue and organ damage, especially in the lungs and the digestive tract... read more

Primary ciliary dyskinesia, including Kartagener syndrome

Alpha-1 antitrypsin deficiency Alpha-1 Antitrypsin Deficiency Alpha-1 antitrypsin deficiency is a hereditary disorder in which a lack or low level of the enzyme alpha-1 antitrypsin damages the lungs and liver. Alpha-1 antitrypsin deficiency is caused by... read more

Marfan syndrome Marfan Syndrome Marfan syndrome is a rare hereditary disorder of connective tissue, resulting in abnormalities of the eyes, bones, heart, blood vessels, lungs, and central nervous system. This syndrome is caused... read more

Immunoglobulin deficiency syndromes

White blood cell dysfunction

Complement deficiencies

Certain autoimmune disorders, such as rheumatoid arthritis Rheumatoid Arthritis (RA) Rheumatoid arthritis is an inflammatory arthritis in which joints, usually including those of the hands and feet, are inflamed, resulting in swelling, pain, and often destruction of joints.... read more , Sjögren syndrome Sjögren Syndrome Sjögren syndrome is a common autoimmune rheumatic disorder and is characterized by excessive dryness of the eyes, mouth, and other mucous membranes. White blood cells can infiltrate and damage... read more , and ulcerative colitis Ulcerative Colitis Ulcerative colitis is a chronic inflammatory bowel disease in which the large intestine (colon) becomes inflamed and ulcerated (pitted or eroded), leading to flare-ups (bouts or attacks) of... read more

Human immunodeficiency virus (HIV) infection Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS). HIV is transmitted... read more

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