(See also Overview of Idiopathic Interstitial Pneumonias.)
The disease usually begins between the ages of 40 and 60 and affects men and women equally. Cigarette smoking does not appear to increase the risk of developing cryptogenic organizing pneumonia.
Almost 75% of people have progressively worsening cough and shortness of breath upon exertion, typically for less than 2 months before seeking medical attention. A flu-like illness, with a cough, fever, a feeling of illness (malaise), fatigue, and weight loss, heralds the onset in about 50% of people.
Doctors do not find any specific abnormalities on routine laboratory tests or on a physical examination, except when doctors listen to the lungs with a stethoscope they frequently hear crackling sounds and occasionally squeaking sounds as the person inhales. Pulmonary function testing usually shows that the amount of air the lungs can hold is below normal. The amount of oxygen in the blood is often low at rest and is even lower during exercise.
A chest x-ray can help doctors make the diagnosis, but it is often not conclusive. Computed tomography (CT) may be done, and sometimes the findings are typical enough to allow doctors to make a diagnosis without ordering additional tests.
In other cases, to confirm the diagnosis, doctors do a lung biopsy using a bronchoscope. Many times, a larger sample is needed and must be removed surgically.