Lung fibrosis (also called pulmonary fibrosis, PF) is a condition where scar tissue builds up in the lungs. This causes the lungs to become stiff, reduces gas exchange, and leads to a restrictive lung defect. Patients usually present with progressive SOB (shortness of breath), reduced exercise tolerance, and often a dry cough.

PF is part of the wider group of interstitial lung diseases (ILDs). There are >200 possible causes, including autoimmune disease, occupational or environmental exposure, infection, radiotherapy, and adverse drug reactions. When no cause is found after appropriate assessment, it is called idiopathic pulmonary fibrosis (IPF).

This is an important primary care topic. GPs need to suspect lung fibrosis early, look for associated causes, identify possible drug triggers, arrange initial investigation, and make a timely respiratory referral. Delay in recognition can lead to missed opportunities for earlier diagnosis, supportive care, and disease-specific treatment.

For the RCGP AKT, lung fibrosis may appear as:

• Restrictive spirometry interpretation

• Differential diagnosis of chronic breathlessness

• Recognition of drug-induced lung disease

• Choosing the right referral pathway

Pulmonary fibrosis (PF) develops after repeated injury to alveolar epithelium (air-sac lining) followed by abnormal wound repair. This drives fibroblast activation and excess extracellular matrix deposition, leading to progressive scarring, stiff lungs, ↓ compliance, and impaired gas exchange. PF sits within the wider interstitial lung disease (ILD) group, which includes >200 disorders causing fibrosis, inflammation, or both.

Classification of Causes

Pulmonary fibrosis is best approached by cause. In primary care, think of 6 broad groups: idiopathic, autoimmune, occupational/environmental, hypersensitivity pneumonitis, drug/radiation-related, and other specific ILDs. The key task is to spot possible fibrosis early, look for a trigger, and refer promptly when ILD (interstitial lung disease) is suspected. The RCGP curriculum specifically includes “lung fibrosis and associated causes, including adverse drug reactions” under Respiratory Health.

Epidemiology and risk factors
IPF usually affects adults >60 years and is more common in men. In primary care, NICE recommends considering IPF in people >45 years with persistent exertional breathlessness or cough. Important risk factors include smoking, family history/genetic susceptibility, occupational dust exposure (for example asbestos or silica), environmental antigen exposure causing hypersensitivity pneumonitis, autoimmune disease, and drug or radiation exposure.

Clinical presentation in primary care

Think of lung fibrosis in any patient aged >45 years with persistent exertional SOB + dry cough, especially if there are fine bibasal inspiratory crackles, clubbing, or normal / restrictive spirometry. NICE recommends considering IPF in this group and arranging CXR or respiratory referral.

High-yield clues

• Gradual breathlessness over months

• Dry cough

• “Velcro” bibasal crackles

• Clubbing may be present

• FEV₁/FVC preserved or ↑ with FVC ↓

• Ask about drugs, dusts, birds, mould, and autoimmune symptoms

Autoimmune disease and pulmonary fibrosis

Think of CTD-ILD when a patient has chronic SOB + dry cough with clues to autoimmune disease such as joint pain, Raynaud’s, sicca symptoms, skin thickening, myositis, rash, or mechanic’s hands. Key causes are RA, systemic sclerosis, Sjögren’s, myositis/antisynthetase syndrome, MCTD, and SLE. Lung disease may precede the systemic diagnosis. In RA, also consider methotrexate pneumonitis. Early respiratory ± rheumatology referral is important.

Investigations in Primary Care

Aim

In primary care, investigations help you to:

• support suspicion of ILD / pulmonary fibrosis

• look for a possible cause

• identify severity

• decide on urgent respiratory referral

Definitive diagnosis usually needs HRCT and specialist MDT review.

High-yield tests

• Spirometry: may show a restrictive pattern

• Pulse oximetry: check for resting or exertional desaturation

• CXR: may show reticular change or may be normal

• Bloods: FBC, CRP/ESR, renal, liver, and autoimmune tests if CTD-ILD is possible

• DLCO / gas transfer: useful, but usually part of full PFTs in secondary care

Spirometry interpretation

Parameter	Typical restrictive finding
FEV₁	↓
FVC	↓↓
FEV₁/FVC ratio	Normal or ↑
Overall pattern	Restrictive defect

A restrictive pattern is suggested when FVC is low but the FEV₁/FVC ratio is preserved or raised. This differs from obstructive disease, where the ratio is reduced. Spirometry can suggest restriction, but true restriction is confirmed by full lung volumes, not spirometry alone.

Investigations in primary care should include a focused history and examination, spirometry, pulse oximetry, CXR, and basic blood tests. Ask about smoking, occupation, birds, mould, medications, and autoimmune features. Spirometry may show a restrictive pattern with FVC ↓ and FEV₁/FVC preserved or ↑, but normal spirometry does not exclude early ILD. CXR may be abnormal or normal, so ongoing suspicion should still prompt respiratory referral. Definitive assessment usually requires HRCT and full pulmonary function testing, including DLCO, in secondary care.

Management is mainly secondary-care led. In general practice, the priorities are early suspicion, prompt respiratory referral, smoking cessation, review of culprit drugs and exposures, vaccination, and supportive care. Patients with suspected IPF should be referred to a respiratory specialist, and diagnosis should be confirmed by an ILD MDT. Specialist treatment may include pirfenidone or nintedanib, pulmonary rehabilitation, oxygen therapy, palliative care, and lung transplant assessment in selected cases.

Conclusion

Pulmonary fibrosis is an important primary care differential in adults with progressive exertional breathlessness, dry cough, fine bibasal inspiratory crackles, or unexplained restrictive spirometry. The key GP task is not to confirm the exact subtype, but to recognise possible ILD early, identify associated causes such as occupational exposure, autoimmune disease, and culprit drugs, and arrange timely respiratory referral. A careful history of work, environment, medications, and systemic symptoms is often the clue to diagnosis. Because management is largely specialist-led and multidisciplinary, primary care should focus on early suspicion, initial investigation, supportive care, vaccination, smoking cessation, comorbidity management, and safety-netting. In progressive disease, GPs also play an important role in ongoing support and palliative care planning.

Key curriculum connections

Curriculum area	Why it matters in lung fibrosis
Occupational history	Essential in any patient with chronic breathlessness; ask about asbestos, silica, coal, beryllium, farming, birds, mould
Connective tissue disease	ILD may be linked to RA, systemic sclerosis, Sjögren’s, myositis, SLE; systemic clues may be subtle
Drug-induced disease	Important AKT and clinical topic; think amiodarone, nitrofurantoin, methotrexate, bleomycin
Spirometry interpretation	Recognise a restrictive pattern: FVC ↓, FEV₁ ↓, FEV₁/FVC normal or ↑
Referral pathways	Suspected ILD / IPF needs early respiratory referral and usually MDT diagnosis
Multidisciplinary care	Management often involves GP, respiratory physician, radiologist, rheumatologist, ILD MDT, palliative care team
Occupational disease support	Patients with asbestosis or pneumoconiosis may need signposting for benefits / compensation advice
Palliative care	Progressive fibrotic lung disease may require symptom control, advance care planning, and end-of-life support

• Tolle LB, Southern BD, Culver DA, Horowitz JC. Idiopathic pulmonary fibrosis: what primary care physicians need to know. Cleveland Clinic Journal of Medicine. 2018;85(5):377‑386.

• Pulmonary Fibrosis Foundation. Drug‑induced pulmonary fibrosis. Accessed 2026.

• Medsafe (New Zealand Medicines and Medical Devices Safety Authority). Medicine‑induced interstitial lung disease. Safety communication.

• National Institute for Health and Care Excellence (NICE). Idiopathic pulmonary fibrosis in adults: diagnosis and management (CG163). Clinical guideline.

• Early recognition of interstitial lung disease. Review article highlighting the need for early suspicion and referral.

• Methotrexate‑induced pneumonitis case report. Describes clinical features and management.

• Physio‑pedia. Pulmonary fibrosis.

• GP Training Schemes. Respiratory medicine in general practice.

• Wang Y, et al. Pulmonary fibrosis: pathogenesis and therapeutic strategies. MedComm. 2024.

• Asthma + Lung UK. Drug‑induced interstitial lung disease.

• Royal College of General Practitioners (RCGP). Respiratory health curriculum guide.

• Sankari A, et al. Idiopathic pulmonary fibrosis. StatPearls.

• Pulmonary Fibrosis Foundation. Drug‑Induced.

• Action for Pulmonary Fibrosis. What is drug‑induced pulmonary fibrosis?

• Radiopaedia. Drug‑induced lung disease.

• BMJ Best Practice. Idiopathic pulmonary fibrosis.

• GPnotebook. Classification into upper and lower lobe fibrosis – mnemonics.

• Fisher A, Brown KK, du Bois RM, et al. Connective tissue disease‑associated interstitial lung disease. Current Respiratory Care Reports.

• Spirometry.com. Understanding restrictive lung disease with spirometry.

• eMedicine (Medscape). Hypersensitivity pneumonitis.

• American Thoracic Society. Connective tissue‑related interstitial lung disease primer.

• Wikipedia. Hypersensitivity pneumonitis.

• Patient.info. Hypersensitivity pneumonitis.

• Tyagi N, Sankari A. Restrictive lung disease. StatPearls.

• NICE Technology Appraisal (TA864). Nintedanib for treating idiopathic pulmonary fibrosis.

• Pneumoconiosis.org.uk. Types of pneumoconiosis.

• British Thoracic Society (BTS). Clinical statement on pulmonary sarcoidosis.

• Wikipedia. Pneumoconiosis.

• StatPearls. Pneumoconiosis.

• UK Government. Review and update of the prescription for prescribed disease D1 pneumoconiosis.

• Kadura S, Raghu G. Rheumatoid arthritis‑interstitial lung disease. European Respiratory Review.

• American Thoracic Society Journals. Idiopathic pulmonary fibrosis/usual interstitial pneumonia.

• 6Patterns.org. Usual interstitial pneumonia.