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Symptoms and Signs of Interstitial Lung Disease

Doctor's Notes on Interstitial Lung Disease

Interstitial lung disease is inflammation in the interstitial tissue of the lungs, the spaces and supportive tissue that surround and separate the air sacs (alveoli), and not the air sacs themselves. Interstitial inflammation typically occurs all over the lungs and is not confined to one location.

Symptoms of interstitial lung disease develop gradually as a result of decreased lung function and may include shortness of breath, dry cough, and signs of chronically reduced oxygen levels in the blood such as clubbing (a painless enlargement of the fingertips) and an enlarged heart. Complications of interstitial lung disease include pulmonary hypertension (a type of high blood pressure that affects the arteries within the lungs), right-sided heart failure (cor pulmonale), and respiratory failure, which can be fatal.

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 3/11/2019

Interstitial Lung Disease Symptoms

Decreased lung function is the result of the inflammation present in the supporting interstitial tissues, which leads to scarring and thickening. This is because the thickened and stiff tissues cannot breathe as effectively as healthy lung tissue. Symptoms, therefore, are related to the reduced efficiency of breathing and corresponding reduced levels of oxygen in the blood.

The symptoms depend to a certain extent upon the exact cause of the condition, but shortness of breath and a dry cough are the most common symptoms. In most cases, these symptoms develop gradually. Signs of chronically reduced oxygen levels in the blood include clubbing (a painless enlargement of the fingertips) and an enlarged heart.

Interstitial lung disease can lead to serious long-term complications. Pulmonary hypertension, a type of high blood pressure that affects the arteries within the lungs, may develop. Ultimately, right-sided (the side of the heart that pumps blood back to the lungs to receive oxygen) heart failure may result (known as cor pulmonale). Respiratory failure is a potentially fatal long-term complication of interstitial lung disease.

Interstitial Lung Disease Causes

Interstitial lung disease is felt to be caused by a misdirected immune or healing reaction to a number of factors, including:

  • infections of the lungs;
  • toxins in the environment (such as asbestos, silica dust);
  • certain medications (particularly some drugs used as chemotherapy for cancers);
  • radiation therapy to the chest; and
  • chronic autoimmune diseases: connective tissue diseases such as lupus, scleroderma, and rheumatoid arthritis

Sometimes, the process of inflammation and scarring of the interstitial tissues of the lungs develops in the absence of a known cause. When no cause can be identified, this is referred to as idiopathic (unknown cause) interstitial lung disease or idiopathic pulmonary fibrosis. Depending upon the location, severity, and pattern of lung involvement, the idiopathic interstitial lung diseases have been further subdivided into categories. Examples of different types of idiopathic interstitial lung disease include:

  • usual interstitial pneumonitis (UIP),
  • bronchiolitis obliterans with organizing pneumonia (BOOP),
  • lymphocytic interstitial pneumonitis (LIP), and
  • desquamative interstitial pneumonitis (DIP).

Common Respiratory Illnesses Slideshow

Common Respiratory Illnesses  Slideshow

The body’s respiratory system includes the nose, sinuses, mouth, throat (pharynx), voice box (larynx), windpipe (trachea), and lungs. Upper respiratory infections affect the parts of the respiratory tract that are higher on the body, including the nose, sinuses, and throat, while lower respiratory infections affect the airways and lungs.

Upper Respiratory Infection

Types of upper respiratory infection include the common cold (head cold), the flu, tonsillitis, laryngitis, and sinus infection. Of the upper respiratory infection symptoms, the most common is a cough. Other symptoms of upper respiratory infection may include stuffy or runny nose, sore throat, sneezing, muscle aches, and headache.

Lower Respiratory Infection

Lower respiratory infection can be caused by bronchitis, pneumonia, respiratory syncytial virus (RSV), severe flu, or tuberculosis, for example). Lower respiratory infection symptoms include a severe cough that may produce mucus (phlegm), cause shortness of breath, chest tightness, and wheezing when exhaling.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.