Pulmonary Fibrosis

What Is Pulmonary Fibrosis?

Pulmonary fibrosis means scarring (fibrosis) of the lung tissue. Over time, healthy, elastic lung tissue is replaced by thick, stiff scar tissue. This makes the lungs less able to expand and less able to move oxygen from the air you breathe into your bloodstream — which is why breathlessness is the hallmark symptom.

PF is not a single disease. It is the shared endpoint of many different lung conditions grouped under the umbrella of interstitial lung disease (ILD) — a family of more than 200 disorders that affect the tissue around the lungs' air sacs (alveoli).

Once scarring has formed, it generally cannot be reversed — but modern treatments can slow how quickly the disease progresses, and supportive care can meaningfully improve day-to-day life.

‍

What Causes Pulmonary Fibrosis?

In many patients, no single cause can be identified — this is called idiopathic pulmonary fibrosis (IPF). In others, PF develops as a consequence of an identifiable trigger or underlying condition. Known contributors include autoimmune and connective tissue diseases such as rheumatoid arthritis, systemic sclerosis (scleroderma), and Sjögren's syndrome; long-term environmental or occupational exposures to substances like silica, asbestos, coal dust, hard-metal dust, mouldy hay, or bird proteins (which can cause hypersensitivity pneumonitis); certain medications, including some chemotherapy agents, amiodarone, methotrexate, and nitrofurantoin; prior radiation therapy to the chest; and some chronic infections or the aftermath of severe lung injury, including post-COVID fibrosis in a subset of patients. There is also a clear genetic component: a family history of pulmonary fibrosis is found in a minority of patients, and specific gene variants (such as those affecting MUC5B and telomere-maintenance genes) raise risk. Smoking is a well-established risk factor, particularly for IPF.

Types of Pulmonary Fibrosis

• Idiopathic Pulmonary Fibrosis (IPF) — the most common and most severe form, with no identifiable cause. Typically diagnosed after age 50, more often in men, and defined by a specific scarring pattern (UIP) on CT scan.
• Progressive Pulmonary Fibrosis (PPF) — a non-IPF fibrotic ILD that keeps worsening despite standard treatment. It is a behaviour of the disease rather than a distinct diagnosis, and can develop from many underlying ILDs.
• Connective Tissue Disease-associated ILD (CTD-ILD) — fibrosis arising from an autoimmune disease, e.g. rheumatoid arthritis-associated ILD (RA-ILD) or systemic sclerosis-associated ILD (SSc-ILD).
• Hypersensitivity Pneumonitis (HP) — triggered by repeated inhalation of an allergen (mould, birds, certain dusts); can become fibrotic if exposure continues.
• Sarcoidosis-related fibrosis — a late complication of sarcoidosis.
• Drug- or radiation-induced pulmonary fibrosis — caused by specific medications or chest radiotherapy.
• Pneumoconioses — occupational fibrosis from silica, asbestos, coal dust, and similar exposures.
• Familial pulmonary fibrosis — when two or more close relatives are affected; often linked to inherited gene variants.
• Unclassifiable ILD — when even a multidisciplinary team cannot assign a specific diagnosis.

Getting the specific type right matters, because treatment differs fundamentally between IPF and the other forms.

‍

Treatment Options

There is currently no cure for the scarring itself, but treatment has come a long way. Antifibrotic medicines — pirfenidone and nintedanib — slow how fast lung function declines in IPF and, in the case of nintedanib, in other progressive fibrosing ILDs as well. Immune-modulating medicines (corticosteroids, mycophenolate, azathioprine, rituximab and others) are used for ILDs driven by autoimmune disease or inflammation — but importantly, routine immunosuppression is not recommended in stable IPF, where it can cause harm. Supportive care is just as important as medication: pulmonary rehabilitation (a structured exercise and education programme) improves breathlessness, stamina, and quality of life for almost all patients; supplemental oxygen helps when oxygen levels drop; vaccinations (influenza, pneumococcal, COVID-19) reduce the risk of serious infections; and treating reflux, sleep apnoea, and other comorbidities matters more than many patients realize. For eligible patients with advanced disease, lung transplantation remains the definitive survival-extending option, and early referral for evaluation is recommended rather than waiting until the patient is very unwell. Palliative and symptom-focused care — including low-dose opioids for severe breathlessness — is a legitimate and important part of treatment at any stage, not only at the end of life.