(See also Overview of Idiopathic Interstitial Pneumonias.)
Most people who have nonspecific interstitial pneumonia are women between the ages of 40 and 50. Most have no known cause or risk factor. However, a similar process can develop in people with connective tissue disorders (in particular, systemic sclerosis, polymyositis, or dermatomyositis), in some forms of drug-induced lung injury, and in people with hypersensitivity pneumonitis.
A dry cough and shortness of breath develop over months to years. Low-grade fever and a feeling of illness (malaise) may occur, but high fever, weight loss, and other general symptoms of illness are unusual.
As with other idiopathic interstitial pneumonias, chest x-rays and computed tomography (CT) are done. 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.
Doctors sometimes do bronchoscopy and wash segments of the lung with a salt-water solution and then collect the washings (bronchoalveolar lavage) for testing. More than half of people have more lymphocytes (a type of white blood cell) than normal in the washings.
Lung biopsy is often needed to confirm the diagnosis.
Corticosteroids sometimes together with immunosuppressants are usually effective. Survival depends on how severe the disease is. People with mild disease often survive for at least 10 years after being diagnosed. However, survival declines to 3 to 5 years in people with more severe disease.