Definition & Overview

Interstitial lung disease refers to different lung conditions that have one thing in common: they affect the interstitium, which is a network of tissue that creates a lace-like pattern extending throughout the left and right lungs. The interstitium is made up of tiny blood vessels that allow gas exchange between the blood and the air that travels through the lungs. It is an important support mechanism for the alveoli or the microscopic air sacs in the lungs.

Cause of Condition

Interstitial lung disease comes in many forms, and each form differs based on the cause of the condition. Some of these forms are short-lived and may go away completely, while some are chronic and cause irreversible damage. The different types of the disease include:

  • Interstitial pneumonia – A form of the disease that is caused by a bacterial, viral, or fungal infection affecting the interstitium. Its most common cause, however, is a bacteria called the mycoplasma pneumonia.

  • Idiopathic pulmonary fibrosis – A chronic form of the disease that causes scarring or fibrosis in the interstitium. This is also a progressive condition, and its cause is still unknown.

  • Hypersensitivity pneumonitis – A form of the disease that springs from the continuous inhalation or exposure to a specific irritant, such as mold and dust. The most common causes are silica dust, talc, coal dust, some metals from mining plants, grain dust (commonly used in farming), and bird proteins, especially from exotic birds, chickens, or pigeon species. A specific sub-type of this disease is called the asbestosis, which is caused by exposure to asbestos.

  • Non-specific interstitial pneumonitis – This form often occurs in combination with an autoimmune condition such as scleroderma or rheumatoid arthritis.

  • Cryptogenic organizing pneumonia – Also known as bronchiolitis obliterans, this is a disease similar to pneumonia but is not caused by bacteria.

  • Acute interstitial pneumonitis – A sudden onset of the disease, often in a severe state, that may cause the person to require life support.

  • Desquamative interstitial pneumonitis – A form of the disease that is linked to smoking.

  • Sarcoidosis – Although this is not a form of the disease, it is a condition that often affects the interstitium. Other symptoms of this condition include swollen lymph nodes and possible effects on the heart, skin, nerves, and eyes.

Aside from bacteria, viruses, fungi, and irritants, interstitial lung disease can also be caused by certain drugs, namely nitrofurantoin, amiodarone, and bleomycin, among several others. However, despite all the information present regarding the possible causes of this disease, most cases occur without any obvious and specific cause.

This disease affects both men and women of any age with equal risk. However, it is more common among those who have existing autoimmune diseases.

Key Symptoms

All forms of interstitial lung disease, despite having different causes, are characterized by the thickening of the interstitium. When this occurs, it causes other symptoms, such as inflammation, scarring, and edema.

The earliest sign is shortness of breath, which may be mild at first but may get worse gradually over the course of many months. However, if the disease is related to pneumonia or is an acute form, the symptoms may come on more quickly and may take just hours or days to develop or progress.

These symptoms may also be accompanied by dry and non-productive cough. In some people, especially those with cryptogenic organizing pneumonia, some weight loss may also be observed.

When a person experiences shortness of breath that comes on suddenly and gets worse quickly, or develops and gets worse over time, it is best to seek medical attention. The same advice applies to those who have been suffering from dry cough for a long time with no obvious underlying cause. An interstitial lung disease may be diagnosed after imaging tests are conducted to identify the cause of breathlessness and dry cough.

The tests used to diagnose this disease include:

  • Chest x-ray – The first test used to diagnose shortness of breath or dry cough is a chest x-ray. If fine lines in the lungs are seen on the x-ray results, it is possible that the patient is suffering from interstitial lung disease.

  • CT scan – Computed tomography scan is a more advanced imaging test that takes a series of more detailed images of the lungs and its surrounding structures. This is more effective in detecting interstitial lung disease compared to a standard chest x-ray. If a standard CT scan causes a doctor to suspect interstitial lung disease but more confirmation is required, a high-resolution CT scan will be performed to obtain detailed images of the lungs.

  • Pulmonary function test – This is a special test used to check the condition and capacity of the lungs. This test can determine whether the lungs’ ability to transfer oxygen from the lungs to the blood is compromised in any way. The test is performed by having the patient sit in a fully enclosed plastic booth and breathe through a tube.

  • Biopsy of the lungs – A sample of lung tissue may also be taken for closer examination. This is done for the purpose of determining the specific type of interstitial lung disease that a person is suffering from. A biopsy of lung tissue can be done through a bronchoscopy, a VATS or video-assisted thoracoscopic surgery, or a thoracotomy, also known as an open lung biopsy.

Who to See & Types of Treatments Available

The most common treatments for interstitial lung disease include:

  • Antibiotics – Bacterial infections and interstitial pneumonia can be treated with azithromycin (Zithromax) or levofloxacin (Levaquin), both of which are found effective in eliminating the bacteria that is linked to interstitial lung disease.

  • Oxygen therapy – People whose oxygen levels in the blood are low due to interstitial lung disease may be given inhaled oxygen to improve symptoms and prevent heart damage caused by low oxygen levels.

  • Corticosteroids – Corticosteroids are used when there is inflammation in the lungs and when there is a risk of long-term damage and scarring. Corticosteroids, such as methylprednisone and prednisone, reduce the immune system’s activity so that the inflammation, which the immune system triggers in response to an infection, will be controlled.

  • Lung transplant – If the disease is in its advanced stages when detected or when it has progressed to a more advanced stage despite treatment, a patient may need a lung transplant. Studies show that patients who have undergone lung transplant due to interstitial lung disease experience a significant improvement in their quality of life and also gain a renewed ability to exercise.

  • Behr J. Approach to the diagnosis of interstitial lung disease. Clin Chest Med. 2012;33:1-10.

  • Raghu G. Interstitial lung disease. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 92.

  • Selman M, Morrison LD, Noble PW, King TE. Idiopathic interstitial pneumonias. In: Mason RJ, Murray JF, Broaddus VC, et al., eds. Murray and Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, Pa: Elsevier Saunders; 2010:chap 57.

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