Bronchiolitis Obliterans Organizing Pneumonia (BOOP) is an inflammation of the bronchioles (bronchiolitis) and surrounding tissue in the lungs. Most of the time, the cause of BOOP is not known.
Bronchiolitis – The airways transport air into the lungs. The smallest airways are called bronchioles and are less than one millimeter in diameter. There are over 200,000 of these airways. Sometimes, the surfaces of these small airways become inflamed. This is called bronchiolitis.
Obliterans – Inflammation in these small airways may become of such severity that it occupies the entire airway and obliterates the airway. This is referred to as obliterans.
Organizing – Sometimes, usually after a few days, inflammation cells begin to form a pattern that is referred to as a process that is organizing.
Pneumonia – The lung exchanges oxygen from the air to the blood. The rounded structures where this occurs are called alveoli. There are millions of them. If unfolded, they create an area the size of a tennis court. When these structures fill with inflammation cells, it is called pneumonia.