Diffuse Interstitial Lung Disease
Diffuse interstitial lung disease refers to disease within both lungs that affects the interstitium or connective tissue that forms the support structure of the lungs’ air sacs or alveoli. When you inhale, the alveoli fill with air and pass oxygen to your blood stream. When you exhale, carbon dioxide passes from the blood into the alveoli and is expelled from the body. When interstitial disease is present, the interstitium becomes inflamed and stiff, preventing the alveoli from fully expanding. This limits both the delivery of oxygen to the blood stream and the removal of carbon dioxide from the body. As the disease progresses, the interstitium scars with thickening of the walls of the alveoli, which further hampers lung function.
Your doctor may use blood tests, pulmonary function testing (spirometry), pulse oximetry, chest x-ray, chest CT, bronchoscopy and biopsy, or surgical biopsy to help diagnose your condition. Treatment depends on the underlying cause of the disease and your health status. Medication, respiratory therapy or surgery may be prescribed to help improve lung function.
What is diffuse interstitial lung disease?
Diffuse interstitial lung disease (ILD) is a group of diseases that affect the connective tissue that forms the support structure of the air sacs, or alveoli, of the lungs.
During normal inhalation, the alveoli fill with air. Oxygen within the air passes through the walls of the alveoli into the blood stream. In reverse fashion, carbon dioxide passes from the blood into the alveoli and is exhaled. When affected by an interstitial lung disease, the tissue supporting the air sacs—called the interstitium—becomes inflamed and stiff, making it difficult for air sacs to fully expand and limiting the delivery of oxygen to the body and the removal of carbon dioxide from the body. As an interstitial disease progresses, the supporting tissue scars and thickens the alveolar walls, further decreasing lung function.
Inflammation of the lung can be confined to one or more areas in some cases. However, it is often diffuse, meaning it occurs throughout both lungs. Interstitial lung disease may be caused by autoimmune or inflammatory diseases such as:
- rheumatoid arthritis
- scleroderma (systemic sclerosis)
- polymyositis and dermatomyositis (an inflammatory disease that causes muscle weakness)
It may be caused by drug exposure, such as:
- a chemotherapy agent
- antiarrythmic (used to treat irregular heart rhythms)
- statin (used to lower cholesterol levels)
Or, it may be caused by inhaling a substance, such as
- animal protein
Some forms of interstitial pneumonia are related to the inhalation of cigarette smoke and occur as a spectrum of injury that includes respiratory bronchiolitis-interstitial lung disease and desquamative interstitial pneumonia.
In some cases, an interstitial lung disease may be associated with a collection of inflammatory cells (granuloma) such as sarcoidosis. Other diseases in this group include idiopathic pulmonary fibrosis (IPF), acute interstitial pneumonia (AIP), cryptogenic organizing pneumonia (COP) and non-specific interstitial pneumonia (NSIP). There are also many other causes of interstitial lung disease.
Shortness of breath and a dry cough are the most common symptoms of diffuse interstitial lung disease. As the disease progresses, weight loss, muscle and joint pain and fatigue may also occur. At a more advanced stage, individuals may develop an enlarged heart, enlargement of the fingertips (clubbing), and cyanosis (blue coloration in the lips, skin and fingernails as a result of reduced oxygen levels in the blood).
How is diffuse interstitial lung disease evaluated?
To determine the cause of interstitial lung disease, a physician may perform a physical examination and order diagnostic tests, including:
- Blood tests: These tests may help identify autoimmune diseases such as scleroderma and rheumatoid arthritis which can result in interstitial lung disease.
- Spirometry: This is a test of lung function, in which the patient exhales quickly and forcefully through a tube connected to a machine that measures how much air the lungs can hold and how quickly the air moves in and out of the lungs. Spirometry can help determine if there is a problem getting air into the lungs (restriction, such as fibrosis) or out of the lungs (obstruction, such as asthma).
- Pulse oximetry: This test uses a small device placed on a finger tip to measure the oxygen saturation of the blood. It shines a specific wavelength of light though the end of the finger to painlessly measure the amount of oxygen in the blood.
- Chest x-ray: The patterns of lung damage associated with various types of interstitial lung disease are often identifiable on chest x-rays. Chest x-rays may also be used to track the progression of interstitial lung disease. See the Safety page for more information about x-rays.
- CT imaging of the chest: Computed tomography (CT), including a specific technique known as high resolution CT, is used to see the fine detail of the interstitium where interstitial disease occurs. Based on the imaging appearance, a diagnosis (such as idiopathic pulmonary fibrosis) can sometimes be confirmed, potentially avoiding the need for lung biopsy. A CT scan can also often help determine the extent of damage to the lungs, guide biopsy, if needed, and determine appropriate treatment(s). See the Safety page for more information about x-rays.
- Bronchoscopy and biopsy: In this procedure, a very small sample of tissue is removed from the lung using a small, flexible tube called a bronchoscope that is passed through the mouth or nose and into the lungs.
- Surgical biopsy: A surgical biopsy is often needed to obtain a larger sample tissue than is possible with bronchoscopy. During this procedure, surgical instruments and a small camera are inserted through two or three small incisions between the ribs, allowing a physician to see and remove tissue samples from the lungs.
How is diffuse interstitial lung disease treated?
Treatment depends on the cause of the disease and the health status of the patient. Drugs may be prescribed to reduce inflammation in the lungs and/or to suppress the immune system.
This page was reviewed on June 19, 2015