Interstitial lung disease

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Overview

In interstitial lung disease, inflammation and/or scarring (fibrosis) occurs in the interstitium of the lung. The interstitium of the lung refers to the microscopic area within the walls of the alveoli (air sacs) between the membrane of the air sac and the membrane of the surrounding blood vessels. Like the leaves on a tree, the alveoli arise from the tiniest bronchioles (airways).

There are hundreds of millions of alveoli in a lung: more than a couple would fit on the period at the end of this sentence. Each alveolus (individual air sac) is surrounded by a network of tiny blood vessels (capillaries) — like mesh encircling the alveolus. The air sac and blood vessels together are called a respiratory unit. This is where the exchange of oxygen and carbon dioxide takes place.

Normally, oxygen passes easily from inside the air sac, through its membrane, across the interstitium and through the membrane of the blood vessel in which red blood cells are lined up and ready to be loaded with oxygen like empty train cars waiting to be filled with cargo. In interstitial lung disease, inflammation, scarring or fibrosis thickens the interstitium, making the lung thick and restricted from filling to their normal capacity and preventing oxygen from passing freely into the bloodstream.


Symptoms

Shortness of breath, especially with activity.

Dry, hacking cough that does not produce phlegm.

Extreme tiredness and weakness.

Loss of appetite.

Unexplained weight loss.

Discomfort in the chest.

Labored breathing, which may be fast and shallow.

Bleeding in the lungs.

Causes

The lungs contain tiny air sacs (alveoli), which is where oxygen is absorbed. These air sacs expand with each breath.


The tissue around these air sacs is called the interstitium. In people with interstitial lung disease, this tissue becomes stiff or scarred, and the air sacs are not able to expand as much. As a result, not as much oxygen can get to the body.


ILD can occur without a known cause. This is called idiopathic ILD. Idiopathic pulmonary fibrosis (IPF) is the most common disease of this type.


There are also dozens of known causes of ILD, including:


Autoimmune diseases (in which the immune system attacks the body) such as lupus, rheumatoid arthritis, sarcoidosis, and scleroderma.

Lung inflammation due to breathing in a foreign substance such as certain types of dust, fungus, or mold (hypersensitivity pneumonitis).

Medicines (such as nitrofurantoin, sulfonamides, bleomycin, amiodarone, methotrexate, gold, infliximab, etanercept, and other chemotherapy medicines).

Radiation treatment to the chest.

Working with or around asbestos, coal dust, cotton dust, and silica dust (called occupational lung disease).

Infection and partial recovery from diseases like COVID-19.


Risk factors

Interstitial lung disease can be caused by long-term exposure to hazardous materials, such as asbestos. Some types of autoimmune diseases, such as rheumatoid arthritis, also can cause interstitial lung disease. In some cases, however, the causes remain unknown. Once lung scarring occurs, it's generally irreversible.

The risk of interstitial lung disease development increases with age, and the risk was 6.9 times higher (95% CI: 5.9–8.0) in those aged over 70 than in their forties.

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Complications

High blood pressure in your lungs (pulmonary hypertension). Unlike systemic high blood pressure, this condition affects only the arteries in your lungs. ...

Right-sided heart failure (cor pulmonale). ...

Respiratory failure.

Prevention

There is no way to prevent idiopathic or genetic ILD, but it is possible to prevent some of the types with known causes. You can reduce your risk by: Wearing a respirator (a mask that filters particles from the air) around harmful substances, such as asbestos, metal dusts or chemicals. Quitting smoking.

The chance of recovering or ILD getting worse depends on the cause and how severe the disease was when it was first diagnosed.

Some people with ILD develop heart failure and high blood pressure in the blood vessels of their lungs (pulmonary hypertension).

Idiopathic pulmonary fibrosis has a poor outlook.