Interstitial pneumonia, also called interstitial pneumonitis, is a chronic disease of the lungs that is usually caused by a virus or a bacterial infection. The disease is characterized by an inflammation in the interstitial tissue of the lungs — the tissue that lines and supports the tiny air sacs in the lungs called the alveoli. The inflammation typically spreads throughout the surrounding connective tissue in the lungs, and is not normally found in a specific section of tissue, or in the air sacs themselves. It does, however, thicken and stiffen the interstitial tissue supporting the sacs, which is normally highly elastic. That, in turn, makes the air sacs more stiff as well, which makes it harder for oxygen to enter. This results in a slowly progressive shortness of breath and, often, scarring of the interstitial tissue and the air sacs.
There are varying types, levels and degrees of interstitial pneumonias. Some of these types include acute, desquamative, lymphocytic, and nonspecific. The most common form, however, is usual interstitial pneumonia (UIP). The prognosis varies with each type of pneumonia and ranges greatly, from excellent to fatal.
Symptoms of the disease also vary among the different types. The most common symptoms, however include cough and shortness of breath. Other common symptoms include a fever with chills and chest pain. More unusual symptoms include sputum that is sometimes filled with blood, dry crackling and wheezing sounds from the lungs, and cyanosis — a blue coloration of the skin and mucous membranes due to a lack of oxygen in the blood.
Physicians typically diagnose the condition by taking the patient's medical history and conducting a physical exam. A chest X-ray is usually ordered, and if interstitial pneumonia is present, it will show what looks like hazy, ground glass with linear white patches. A pulmonary function test may be conducted to determine whether there is a decrease in the capacity of the lungs, and a lung biopsy may also be performed.
Some people have a higher risk for developing the condition than others. The elderly and those who work or worked in industries where they may have been exposed to pollutants and other environmental toxins often have a higher chance of developing this type of pneumonia. For people who have a family history of lung disease, were or are smokers, or have gastroesophageal reflux disease (GERD), interstitial pneumonia may be more likely as well.
Fortunately, most cases of interstitial pneumonia can be successfully treated with antibiotics and corticosteroids. Antibiotics fight the infection while corticosteroids help reduce the infection. In severe cases, treatment may include hospital admission for oxygen administration, IV fluids and ventilation.