On this page
What is Pulmonary Fibrosis?
Pulmonary fibrosis is a chronic, progressive respiratory disease in which the normal, elastic lung tissue is gradually replaced by stiff, fibrotic scar tissue. This irreversible structural change prevents the lungs from functioning normally, making it increasingly difficult to breathe and transfer oxygen into the bloodstream.
Pulmonary fibrosis is part of the broader family of interstitial lung diseases (ILDs), which are conditions affecting the lung interstitium. This is the delicate network of tissue surrounding the air sacs, or alveoli, where gas exchange occurs.
Forms of Pulmonary Fibrosis
Pulmonary fibrosis is classified into two broad categories based on whether a cause can be identified:
- Idiopathic pulmonary fibrosis (IPF): The most common form, occurring without any identifiable underlying cause. It is a diagnosis of exclusion and carries a particularly poor prognosis.
- Secondary pulmonary fibrosis: Fibrosis with a known or strongly suspected contributing cause (infections, autoimmune diseases, occupational exposures, medications, etc.)
Key Symptoms
The main symptoms with which pulmonary fibrosis typically presents include:
- Dyspnea (breathlessness, a sensation of “air hunger” or difficulty breathing)
- Dry, non-productive cough
- Wheezing (high-pitched whistling sound when breathing)
- Chest pain
Diagnosis
Pulmonary fibrosis can be diagnosed through:
- Medical history (anamnesis) and physical examination
- Imaging studies: chest X-ray and CT scan (the gold standard)
- Pulmonary function tests: spirometry and arterial blood gas analysis (ABG)
- Lung biopsy (in selected cases)
Prognosis
Unfortunately, pulmonary fibrosis currently has no cure. It is a progressive disease with symptoms that worsen over time, eventually causing chronic respiratory failure, which is the most common cause of death. However, available treatments can:
- Alleviate symptoms and improve quality of life
- Slow disease progression in some patients
- Reduce acute exacerbations and hospitalizations
- Prolong survival
The 5-year survival rate varies between 30% and 50%, though outcomes differ considerably based on the specific type and underlying cause of fibrosis, as well as the patient’s response to treatment.
Causes
Epidemiology
Pulmonary fibrosis is a relatively common condition, affecting approximately 30 per 100,000 people worldwide. In Europe, the prevalence is estimated at up to 10 per 100,000.
The disease most commonly affects individuals between 30 and 60 years of age and is more prevalent in men than women. This difference likely reflects greater occupational exposure to known risk factors rather than an intrinsic biological difference.
Etiological Classification
Known causes of secondary pulmonary fibrosis include:
1. Inhalation of harmful substances:
- Inorganic dusts: Silica, which causes silicosis; asbestos, which causes asbestosis; and other heavy metal particles are among the most well-established occupational causes
- Organic dusts: Found in agricultural environments or animal farming, these can cause hypersensitivity pneumonitis (also known as extrinsic allergic alveolitis). Examples include conditions such as “farmer’s lung” and “bird fancier’s lung”
- Cigarette smoke: One of the most significant modifiable risk factors
2. Medications:
- Chemotherapy agents: Bleomycin, cyclophosphamide, methotrexate
- Certain antibiotics: Nitrofurantoin, amiodarone
- Certain anti-inflammatory and biological agents: Rituximab, sulfasalazine
3. Radiation therapy:
- Chest radiotherapy for lung cancer, breast cancer, lymphoma, or other thoracic malignancies can cause radiation-induced pulmonary fibrosis, typically developing 6 months to several years after treatment
4. Systemic and autoimmune diseases:
- Autoimmune/connective tissue diseases: Rheumatoid arthritis, systemic lupus erythematosus, scleroderma, Sjögren’s syndrome
- Sarcoidosis: A multi-system inflammatory disease that commonly involves the lungs
5. Respiratory infections:
- Viral: Cytomegalovirus (CMV), Epstein-Barr virus, and, as the COVID-19 pandemic has shown, SARS-CoV-2 can leave fibrotic sequelae in the lung tissue
- Bacterial: Mycobacterium tuberculosis and other atypical mycobacteria
- Fungal and parasitic: In immunocompromised patients
How Fibrosis Develops in the Lung
Regardless of the specific underlying cause, the fundamental pathological process in pulmonary fibrosis involves:
- Repeated alveolar epithelial injury from the causative agent
- Activation of fibroblasts and myofibroblasts, the key effector cells that deposit collagen, plays a critical role in tissue repair and fibrosis
- Abnormal collagen deposition associated with chronic inflammation
- Progressive architectural distortion of the lung parenchyma
These processes lead to the following physiological consequences:
- Increased work of breathing: Stiffer lungs require more muscular effort to expand
- Increased respiratory rate (tachypnea): The body compensates by breathing faster with shallower breaths
- Hypoxemia: Reduced oxygen concentration in the blood due to impaired gas exchange at the alveolar level
- Hypercapnia: Increased CO₂ in the blood in advanced stages when ventilatory compensation fails
Risk Factors
The most important risk factors associated with pulmonary fibrosis include:
- Smoking: The single most significant modifiable risk factor. People who smoke now or have smoked in the past face approximately double the risk of developing pulmonary fibrosis compared to those who have never smoked
- Age: Risk increases substantially after age 65; IPF is particularly a disease of older adults
- Occupational exposure: Workers in the following fields carry elevated risk:
- Farming and agricultural workers
- Metal industry workers
- Miners
- Construction workers (carpenters, masons, sandblasters)
- Due to exposure to metal dust, wood dust, silica, coal, and asbestos
- Previous chest radiation therapy: For lung, breast cancer, or lymphoma
- Family history: A familial form of pulmonary fibrosis exists. Having an affected first-degree relative significantly increases risk. Multiple genetic variants (in genes encoding telomerase, surfactant proteins, and mucin) have been identified in familial IPF
- Lung infections: Particularly CMV pneumonitis and tuberculosis
- Gastroesophageal reflux disease (GERD): Increasingly recognized as a potential risk factor, micro-aspiration of gastric acid droplets reaching the alveoli may cause repeated sub-clinical lung injury, contributing to fibrosis over time
Symptoms
The symptoms of pulmonary fibrosis develop insidiously and worsen progressively over time. Early symptoms are often attributed to aging or deconditioning, leading to diagnostic delays of months to years.
Primary Symptoms
1. Dyspnea (Shortness of Breath) The cardinal symptom of pulmonary fibrosis, characterized by a distressing sensation of air hunger:
- Exertional dyspnea: Present in early disease, triggered by physical activity such as climbing stairs or walking quickly. Patients often unconsciously reduce their activity levels to avoid breathlessness, masking the symptom’s progression
- Dyspnea at rest: Emerges in advanced disease and indicates severely compromised lung function
2. Dry, Non-Productive Cough A persistent, irritating cough that produces no sputum. It can be debilitating and significantly impacts quality of life and sleep.
3. Wheezing A high-pitched whistling sound during breathing, caused by narrowed or partially obstructed airways.
4. Chest Pain or Tightness A sense of tightness or discomfort in the chest, often worsening with deep breaths.
5. Fatigue and Malaise Profound and often debilitating fatigue occurs, partly due to the increased muscular work of breathing and partly due to chronic hypoxemia.
6. Decreased Appetite and Unintentional Weight Loss Common as the disease progresses, reflecting increased metabolic demands and reduced caloric intake.
Less Common Symptoms
- Low-grade fever: Particularly in secondary forms associated with autoimmune or infectious causes
- Muscle aches and joint pain: Common when fibrosis is associated with connective tissue diseases
- Hemoptysis: Coughing up blood, which is relatively rare in fibrosis, requires immediate medical evaluation to exclude other serious causes.
Important: If you experience progressive shortness of breath, a persistent dry cough lasting more than 3 weeks, or any combination of the above symptoms, seek medical evaluation promptly. Early diagnosis significantly expands treatment options.
Complications
As pulmonary fibrosis progresses, a series of serious complications can develop that further compromise the patient’s respiratory function and quality of life:
-
Hypoxemia and hypercapnia: Respectively, reduced oxygen and elevated carbon dioxide in the arterial blood, assessed by arterial blood gas (ABG) analysis. These worsen progressively as gas exchange capacity deteriorates.
-
Pneumothorax: Abnormal accumulation of air in the pleural space (between the lung and chest wall), preventing normal lung expansion. This is a potentially life-threatening emergency.
-
Cyanosis: Bluish discoloration of the skin, lips, and mucous membranes due to severely reduced blood oxygen saturation.
-
Hypertrophy of accessory breathing muscles: The body recruits additional muscles (neck, shoulders) to assist breathing, which is a visible sign of severe respiratory distress.
-
Pulmonary hypertension: Increased blood pressure in the pulmonary arteries, developing as a consequence of chronic hypoxia causing vasoconstriction and vascular remodeling. This places additional strain on the right side of the heart, eventually leading to cor pulmonale (right heart failure)
-
Digital clubbing (hippocratic fingers): Progressive, painless widening and rounding of the fingertips and toenails. This is a classical sign of chronic hypoxemia and is also seen in other lung and heart diseases.
These complications, together with chronic respiratory failure, are the ultimate cause of death in most patients with advanced pulmonary fibrosis.
Diagnosis
When pulmonary fibrosis is clinically suspected, a structured diagnostic pathway should be followed:
1. Medical History (Anamnesis)
A thorough history is essential and should address:
- Occupational history: Current and past jobs, especially those involving exposure to organic or inorganic dusts (e.g., silica, asbestos, metal, wood, coal), bird droppings, or mold
- Smoking history: Pack-years of smoking, current status
- Family history: Cases of pulmonary fibrosis or other interstitial lung diseases in relatives
- Medication history: Current and past use of chemotherapy agents, amiodarone, nitrofurantoin, biologics
- Previous chest radiation therapy
- History of chronic lung diseases: Emphysema, COPD, recurrent pneumonia
- Autoimmune symptoms: Joint pain, skin rashes, dry eyes/mouth, Raynaud’s phenomenon
2. Physical Examination
- Auscultation: The hallmark finding of pulmonary fibrosis is bilateral, basal “Velcro” crackles (fine inspiratory crackles resembling the sound of tearing Velcro), caused by the sudden opening of fibrotic alveoli
- Breathing pattern: Increased respiratory rate (tachypnea) with shallow breathing
- Signs of hypoxemia: Cyanosis, digital clubbing
- Signs of cor pulmonale: Raised jugular venous pressure, peripheral edema
3. Arterial Blood Gas (ABG) Analysis
- Early disease: Hypoxemia with normal CO₂ (normocapnia). The patient hyperventilates to compensate for low oxygen, blowing off CO₂
- Advanced disease: Both hypoxemia and hypercapnia indicate ventilatory failure
- In patients with only exertional dyspnea, resting ABG may be normal; an exercise oximetry test may unmask desaturation with activity
4. Imaging Studies
Chest X-ray:
- May raise the initial suspicion. Characteristic findings include a bilateral basal “honeycomb” pattern or ground-glass opacities and reticular shadows.
- However, sensitivity and specificity are limited. A normal chest X-ray does not exclude pulmonary fibrosis.
High Resolution CT (HRCT) of the Chest: The Gold Standard
- The most important diagnostic tool for pulmonary fibrosis
- Can detect fibrotic changes even before symptoms develop (early diagnosis)
- Accurately characterizes the morphological pattern and distribution of lesions. For example, UIP (Usual Interstitial Pneumonia pattern) in IPF shows basal-predominant honeycombing with peripheral traction bronchiectasis
- Guides the decision on whether and where to perform a lung biopsy
- Allows assessment of disease activity, progression, and monitoring of treatment response
5. Pulmonary Function Tests
-
Spirometry: Measures lung volumes and airflow. In pulmonary fibrosis, a restrictive pattern is typical. This includes reduced total lung capacity (TLC), forced vital capacity (FVC), and diffusing capacity for carbon monoxide (DLCO). The FEV₁/FVC ratio remains normal or elevated, which helps distinguish it from obstructive diseases like COPD
-
Pulse oximetry: Measures blood oxygen saturation via a finger clip. Normal ≥95%; in pulmonary fibrosis, values frequently fall below 90% at rest or with exertion
-
6-Minute Walk Test (6MWT): This test assesses functional exercise capacity and oxygen desaturation during exercise. It serves as a key parameter for monitoring disease progression and evaluating transplant candidacy
6. Bronchoscopy and Bronchoalveolar Lavage (BAL)
Fiberoptic bronchoscopy allows direct visualization of the airways down to the small bronchi. During the procedure, bronchoalveolar lavage (BAL) can be performed:
- A small volume of sterile saline is instilled into the distal airways and immediately aspirated
- The recovered fluid contains airway cells whose cytological analysis can provide important diagnostic clues about the underlying cause of fibrosis (e.g., a lymphocytic alveolitis suggests hypersensitivity pneumonitis; an eosinophilic pattern suggests eosinophilic pneumonia)
7. Lung Biopsy
When all previous investigations are insufficient to establish a confident diagnosis, surgical lung biopsy (via video-assisted thoracoscopic surgery, VATS) may be required:
- Provides definitive histopathological diagnosis and pattern classification (UIP, NSIP, DIP, etc.)
- Allows precise identification of the type of fibrosis and guides treatment.
- Invasive with a small but real risk of serious complications: hemoptysis, pneumothorax, respiratory decompensation. The indication must be carefully weighed against the patient’s functional status and comorbidities.
8. Genetic Counseling
A significant proportion of pulmonary fibrosis cases have a familial component. Several causative genetic variants have now been identified (in genes encoding telomerase components: TERT, TERC; surfactant proteins: SFTPC, SFTPA2; and mucin: MUC5B).
Genetic counseling can:
- Assess an individual’s probability of carrying a disease-causing mutation
- Enable earlier surveillance and diagnosis in at-risk family members
- Inform reproductive decisions
- Guide emerging targeted therapies
Treatment
The prognosis for pulmonary fibrosis remains guarded. There is currently no treatment that can completely reverse the fibrotic process or cure the disease. However, the therapeutic landscape has evolved substantially, and the goals of modern management are:
- Treat the underlying cause (where identifiable)
- Slow disease progression with antifibrotic drugs
- Manage symptoms and improve quality of life
- Prevent and treat acute exacerbations
- Consider lung transplantation in eligible patients
Treatment of the Underlying Cause
When a specific causative agent or condition is identified:
| Cause | Treatment |
|---|---|
| Occupational dust exposure | Immediate and permanent removal from the exposure environment |
| Organic dust / hypersensitivity pneumonitis | Avoidance of the offending antigen; corticosteroids for acute exacerbations |
| Causative medication | Discontinuation of the offending drug under medical supervision |
| Infectious cause (TB, etc.) | Appropriate antibiotic, antiviral, or antifungal therapy |
| Autoimmune disease | Disease-specific immunosuppressive therapy |
Antifibrotic Drug Therapy for IPF
For idiopathic pulmonary fibrosis (IPF), two antifibrotic medications have been approved and have demonstrated the ability to slow the rate of lung function decline (reduction in FVC decline of approximately 50% compared to placebo):
- Pirfenidone: This medication has anti-inflammatory, antioxidant, and antifibrotic properties. While its exact mechanism is not fully understood, it is known to reduce TGF-β-stimulated fibroblast activity.
- Nintedanib: A tyrosine kinase inhibitor that blocks key growth factors driving fibrosis (PDGF, VEGF, FGF).
Both drugs are taken orally and require careful monitoring for side effects (gastrointestinal effects are most common for both; nintedanib also requires liver function monitoring).
Corticosteroids and Immunosuppressants
When the underlying cause is unknown (idiopathic) or when fibrosis is associated with an autoimmune disease:
-
Corticosteroids (prednisone, dexamethasone): Used primarily for secondary fibrosis associated with autoimmune diseases, and in acute exacerbations of IPF. Their use in pure IPF is increasingly limited given the lack of clear benefit and significant side effect profile.
-
Immunosuppressive agents (cyclophosphamide, mycophenolate mofetil, azathioprine): Used in fibrosis associated with autoimmune diseases; not recommended in IPF without clear autoimmune overlap
Important warning: These medications carry significant potential side effects requiring careful monitoring: osteoporosis, Cushing’s syndrome, bone marrow suppression, renal and hepatic toxicity, obesity, diabetes, and hypertension.
Non-Pharmacological Therapies
Oxygen therapy:
- Supplemental oxygen effectively counteracts the hypoxemia characteristic of pulmonary fibrosis
- Prescribed when resting oxygen saturation falls below 88–90%, or with significant desaturation during exercise
- Available as portable oxygen concentrators for ambulatory patients, significantly improving exercise tolerance and quality of life
Pulmonary Rehabilitation:
- A structured program of supervised aerobic exercise (cycling, walking, swimming) and breathing techniques
- Reduces dyspnea, improves exercise tolerance, and enhances overall quality of life
- Does not slow fibrosis progression but meaningfully improves functional capacity and psychological wellbeing
Management of GERD: Proton pump inhibitors, or PPIs, are often prescribed to reduce micro-aspiration. This is particularly important in patients with documented GERD.
Lung Transplantation
For selected patients who have not responded to medical therapy and have end-stage disease, bilateral lung transplantation represents a life-extending option:
- Eligibility criteria: Age typically <65–70, no significant comorbidities, adequate cardiac function, non-smoking status
- Benefits: Normalization of lung function, improved quality of life, median survival of 5–7 years post-transplant (with some patients surviving >10 years)
- Risks: Major surgery with significant perioperative mortality risk; lifelong immunosuppression with associated infection risks and organ rejection
Transplantation does not cure the underlying genetic or molecular predisposition to fibrosis but provides new, healthy lung tissue.
Follow-Up
Management of pulmonary fibrosis requires close and regular monitoring:
- Every 3–6 months: Clinical assessment, spirometry (particularly FVC and DLCO), pulse oximetry, 6-minute walk test
- Annual HRCT: To assess structural progression
- Arterial blood gas analysis: At each significant clinical change
- Quality of life assessment: Including nutritional status, psychological wellbeing, and need for oxygen therapy adjustment
Prevention
While pulmonary fibrosis cannot always be prevented, especially the idiopathic form, the following measures can significantly reduce the risk of developing preventable forms.
- Stop smoking and avoid passive smoke exposure. This is the most impactful preventive action, as it eliminates the greatest modifiable risk factor.
- Annual influenza vaccination and pneumococcal vaccination: To prevent respiratory infections that can trigger acute exacerbations or contribute to lung damage. COVID-19 vaccination is also strongly recommended.
- Occupational protection measures:
- Wear appropriate respirator masks (FFP2/FFP3 or higher grade) when working in environments with dust, metal particles, or organic materials
- Ensure adequate workplace ventilation
- Comply with occupational health and safety regulations
- Request regular occupational health surveillance if working in high-risk industries
- Treat GERD effectively: To minimize the risk of chronic micro-aspiration
- Genetic counseling for individuals with a family history of pulmonary fibrosis: Enables earlier surveillance and potentially earlier intervention
Sources and Bibliography
- Harrison’s Principles of Internal Medicine, Vol. 1–2, 17th Ed. McGraw Hill, 2009.
- Gramiccioni E, Loizzi M, Foschino Barbaro MP, Resta O, Sollutto F. Malattie dell’apparato respiratorio, 2nd ed. Edizioni Minerva Medica, Torino, 2008.
- American Lung Association: Pulmonary Fibrosis – Types, Causes and Risk Factors
- Raghu G, et al. An Official ATS/ERS/JRS/ALAT Statement: Idiopathic Pulmonary Fibrosis: Evidence-based Guidelines for Diagnosis and Management. Am J Respir Crit Care Med. 2011;183(6):788–824.
- Richeldi L, et al. Efficacy and Safety of Nintedanib in Idiopathic Pulmonary Fibrosis. N Engl J Med. 2014;370(22):2071–2082.
- King TE Jr, et al. A Phase 3 Trial of Pirfenidone in Patients with Idiopathic Pulmonary Fibrosis. N Engl J Med. 2014;370(22):2083–2092.
- European Respiratory Society (ERS): Idiopathic Pulmonary Fibrosis Clinical Practice Guidelines
- National Institute for Health and Care Excellence (NICE): Idiopathic Pulmonary Fibrosis Guideline
- Lederer DJ, Martinez FJ. Idiopathic Pulmonary Fibrosis. N Engl J Med. 2018;378(19):1811–1823.
