Lung scarring, medically termed pulmonary fibrosis, is a condition where lung tissue becomes thickened and stiff over time. This process replaces healthy, flexible air sacs with rigid, non-functional tissue. It arises from various forms of damage and inflammation, leading to permanent changes within the lungs.
How Lung Scarring Develops
Lung scarring begins when lung tissue is injured or chronically inflamed. Normally, the body’s repair mechanisms would heal damaged areas efficiently. However, in pulmonary fibrosis, this healing process malfunctions, leading to an overproduction and excessive deposition of collagen and other fibrous proteins.
Instead of restoring the lung’s original structure, this abnormal repair forms dense scar tissue. This stiff, inelastic tissue replaces healthy, elastic lung tissue essential for breathing. This scar tissue impedes the lungs’ ability to expand and transfer oxygen into the bloodstream, impacting respiratory function.
Underlying Medical Conditions
Several medical conditions can cause inflammation and scarring in the lungs. One such condition is Idiopathic Pulmonary Fibrosis (IPF), a progressive form of lung scarring where the cause remains unknown. IPF is progressive, worsening lung function over time.
Systemic autoimmune diseases can also trigger lung scarring. Conditions like rheumatoid arthritis, systemic sclerosis (scleroderma), lupus, and polymyositis or dermatomyositis involve the immune system mistakenly attacking the body’s own tissues. This immune response can extend to the lungs, causing persistent inflammation and fibrous scar tissue.
Sarcoidosis, an inflammatory disease, commonly affects the lungs by forming tiny clumps of inflammatory cells called granulomas. While granulomas can resolve, some persist and progress, leading to fibrotic changes and permanent lung scarring.
Severe lung infections can cause extensive tissue damage, leading to scarring. Conditions like bacterial pneumonia, tuberculosis, or severe COVID-19 can cause widespread inflammation and lung cell destruction. The healing process may form dense scar tissue, permanently altering lung architecture.
Environmental and Occupational Triggers
Exposure to certain substances in the environment or workplace can also induce lung scarring. Prolonged inhalation of specific particles can lead to chronic inflammation and fibrosis.
Asbestosis is lung scarring caused by inhaling asbestos fibers. Once lodged in the lungs, these fibers cause persistent inflammation and scarring, often in individuals working in construction, shipbuilding, or insulation manufacturing.
Silicosis results from inhaling crystalline silica dust, common in mining, quarrying, sandblasting, and construction. Silica particles trigger an inflammatory response, leading to fibrotic nodules and widespread lung scarring.
Coal worker’s pneumoconiosis, or “black lung disease,” is an occupational lung disease caused by prolonged coal dust inhalation. This dust accumulates in the lungs, causing inflammation and scar tissue that impairs lung function.
Hypersensitivity pneumonitis is an immune-mediated lung disease from repeated inhalation of organic dusts. Examples include mold spores, bird droppings, or agricultural dusts (e.g., from farms or barns). This exposure can provoke an allergic reaction and inflammation in the lungs, which, if chronic, can progress to fibrosis. It is sometimes called “farmer’s lung” or “bird fancier’s lung,” reflecting common exposures.
Medications and Medical Treatments
Certain medical treatments can also cause lung scarring as an unintended side effect. Some medications cause drug-induced lung disease, where the body’s reaction leads to inflammation and fibrosis in the lungs.
Examples of such medications include:
Amiodarone (heart rhythm disorders)
Methotrexate (immunosuppressant)
Bleomycin (chemotherapy)
Nitrofurantoin (antibiotic)
Reactions can be dose-dependent (higher doses/longer use increase risk) or idiosyncratic (unpredictable).
Radiation therapy to the chest for cancer can damage healthy lung tissue within the radiation field. High-energy radiation destroys cancer cells but can injure surrounding lung cells. This injury triggers an inflammatory and repair process, resulting in localized fibrosis and scarring in the irradiated lung portion.