Pulmonary Fibrosis: Scarring of the Lungs

Pulmonary fibrosis describes lasting scar like change within the lung tissue. The lungs become stiffer and oxygen transfer becomes less efficient. Idiopathic pulmonary fibrosis is an important progressive form, but many other fibrotic lung diseases have an identifiable exposure, immune condition or medicine related cause.

What pulmonary fibrosis is Pulmonary fibrosis means that lung tissue has developed persistent fibrotic change. Fibrosis is an abnormal repair response that replaces flexible tissue with stiff collagen rich tissue. The change commonly affects the interstitium surrounding the air sacs and small blood vessels. Pulmonary fibrosis is therefore a description of tissue change rather than one single disease. Interstitial lung disease Interstitial lung disease is usually shortened to ILD. ILD is an umbrella term covering many disorders affecting the supporting tissue around the air sacs. Some ILDs are mainly inflammatory, some are mainly fibrotic and many contain both processes. Not every ILD progresses to extensive fibrosis. Healthy gas exchange Air reaches tiny air sacs called alveoli. Oxygen crosses a very thin barrier from the alveoli into nearby blood vessels. Carbon dioxide travels in the opposite direction and is breathed out. The thin, flexible structure provides a large surface area for efficient gas exchange. How fibrosis changes the lungs Fibrotic tissue thickens and distorts the gas exchange region. The lungs become less compliant, meaning they are harder to expand. Oxygen must cross a less efficient barrier to reach the blood. The amount of functioning lung tissue can also decline as the disease progresses. Fibrosis is not simply an ordinary scar A skin scar usually follows one visible injury and then stabilises. Fibrotic lung disease can involve repeated microscopic injury and abnormal repair across many lung regions. Some conditions stop progressing when the cause is removed or treated. Others continue because the fibrotic process has become self sustaining. Pulmonary fibrosis is not one diagnosis A CT report using the word fibrosis does not establish the exact disease. The same broad appearance can result from autoimmune disease, inhaled exposures, medicines or an idiopathic process. The diagnosis depends on the symptoms and background, imaging pattern, blood tests and specialist discussion. Treatment can differ substantially between causes. Idiopathic pulmonary fibrosis Idiopathic pulmonary fibrosis is usually shortened to IPF. It is the most common idiopathic interstitial pneumonia and the archetypal progressive fibrotic ILD. Idiopathic means that no external exposure, medicine, autoimmune disease or other recognised cause explains the pattern. IPF is diagnosed only after alternative causes have been considered carefully. What happens in IPF Current understanding focuses on repeated injury to the cells lining the alveoli. Abnormal repair signals activate fibroblasts, which produce excessive extracellular matrix and collagen. The lung architecture becomes progressively distorted. IPF is not primarily an infection and is not caused by mucus blocking the airways. Who develops IPF IPF mainly affects older adults and is uncommon below the age of 50. It occurs more often in men and in people who have smoked, although never smokers can develop it. A small minority have another affected family member. Age and smoking increase probability but do not diagnose the condition. Familial pulmonary fibrosis Familial pulmonary fibrosis refers to fibrotic ILD occurring in more than one biologically related family member. Several inherited variants can affect telomeres, surfactant proteins or other repair pathways. A specialist may consider genetic counselling when disease occurs unusually early or clusters within a family. A health problems in the family does not determine the exact course for one person. Fibrosis with an identifiable cause Many people have fibrotic ILD for which an important cause or association can be identified. The broad groups include occupational exposure, environmental antigen exposure, connective tissue disease and medicine related injury. Recognising the cause can change treatment, monitoring and advice for relatives or workplaces. Occupational exposure Repeated inhalation of mineral or industrial dust can injure lung tissue. Asbestos exposure can cause asbestosis, pleural disease and cancer risk. Silica exposure can cause silicosis, particularly in mining, stone cutting and construction. Metal, coal and other workplace dusts can produce additional pneumoconioses. Exposure history matters Clinicians ask about every job, not only the current occupation. Symptoms may appear years or decades after harmful exposure. The assessment includes tasks, dust control, protective equipment and exposure duration. A job title alone cannot measure an individual's dose or prove causation. Hypersensitivity pneumonitis Hypersensitivity pneumonitis is an immune reaction to repeatedly inhaled organic particles. Possible sources include birds, feathers, mould, farming materials and contaminated water aerosols. Some people develop mainly inflammatory disease, while others develop established fibrosis. The responsible antigen is not always identified. Fibrotic hypersensitivity pneumonitis Long term or repeated antigen exposure can produce fibrotic hypersensitivity pneumonitis. The CT distribution and accompanying air trapping clues can differ from classic IPF. Antibody tests can show exposure but do not prove that the antigen caused disease. Diagnosis requires integration of exposure pattern, imaging and sometimes lavage or tissue findings. Connective tissue disease associated ILD Connective tissue diseases can affect the lungs as well as joints, skin and other organs. Important examples include systemic sclerosis, rheumatoid arthritis, inflammatory myositis and Sjögren syndrome. ILD can appear before the autoimmune condition becomes otherwise obvious. Respiratory and rheumatology teams often assess and manage these conditions together. Autoimmune clues Clues can include Raynaud phenomenon, inflammatory joint pain and prolonged morning stiffness. Skin thickening, unusual rashes, dry eyes, dry mouth or muscle weakness can also matter. Blood autoantibodies provide evidence but can be positive in people without active autoimmune disease. The result must be interpreted with symptoms and examination. Drug induced pulmonary fibrosis Some medicines can inflame or damage lung tissue. Recognised examples include amiodarone, nitrofurantoin, bleomycin, methotrexate and several cancer treatments. The pattern, timing and risk differ between medicines. Most people taking these medicines do not develop pulmonary fibrosis. Medicine review must be careful A suspected medicine should not be stopped without urgent clinical discussion unless a severe reaction is occurring. Some medicines are essential for controlling life threatening heart, infection, cancer or inflammatory disease. Clinicians assess timing, alternative causes and the risk of continuing or withdrawing treatment. Radiation related fibrosis Radiotherapy involving the chest can cause lung inflammation followed by fibrosis within the treated region. The pattern usually reflects the radiation field. Symptoms and imaging changes can develop months after treatment. Cancer recurrence, infection and pulmonary embolism remain alternative explanations for new breathlessness. Post infectious and other fibrosis Severe lung injury can leave residual fibrotic change. Examples include acute respiratory distress syndrome and some severe viral pneumonias. Sarcoidosis can also progress to fibrotic lung disease in a minority of people. The presence of fibrosis does not mean that every original inflammatory disease remains active. Progressive pulmonary fibrosis Some fibrotic ILDs other than IPF continue progressing despite appropriate initial management. Progression can involve worsening symptoms, declining lung function and increasing fibrosis on imaging. This behaviour is called progressive pulmonary fibrosis or progressive fibrosing ILD. The label describes behaviour across several underlying diseases rather than replacing the original diagnosis. Common symptoms The most characteristic symptoms are gradually increasing breathlessness during physical activity and a persistent dry cough. Fatigue, reduced stamina and unintended weight loss can occur. Symptoms commonly develop over months or years. Rapid deterioration requires assessment for an acute complication or a different diagnosis. Exertional breathlessness Early disease may be noticeable only when climbing hills or stairs. As gas exchange worsens, ordinary walking and daily tasks become more difficult. Oxygen levels can remain acceptable at rest but fall during physical activity. Breathlessness has many causes and does not identify pulmonary fibrosis alone. Dry cough The cough in IPF is commonly dry and persistent. Some people produce small amounts of sputum because of infection, reflux or coexisting airway disease. A productive cough should prompt assessment for bronchiectasis, infection or another cause. Cough severity does not directly measure the amount of fibrosis. Fatigue and reduced activity Breathing requires more effort when the lungs are stiff. Low oxygen during activity and deconditioning can add to fatigue. Sleep disturbance, anxiety, anaemia and medicines may also contribute. The person can enter a cycle of avoiding activity and losing muscle strength. Fine inspiratory crackles Clinicians may hear fine crackling sounds near the lung bases during inspiration. They are sometimes compared with separating hook and loop fastener. These sounds can occur with pulmonary fibrosis but also with pulmonary oedema and other conditions. Crackles provide a clue rather than a diagnosis. Finger clubbing Finger clubbing causes the fingertips to become rounded and the nail angle to change. It occurs in some people with IPF and other chronic lung diseases. Lung cancer, bronchiectasis, heart disease and gastrointestinal conditions can also cause clubbing. Its absence does not exclude pulmonary fibrosis. Cyanosis Cyanosis means a blue or grey colour affecting lips, tongue or skin because blood oxygen is very low. Skin tone and lighting can alter how visible it appears. Cyanosis with severe breathlessness requires emergency assessment. Pulse oximetry provides useful information but can also be inaccurate. Symptoms can be subtle in older adults A person may reduce walking speed or stop activities before describing breathlessness. They may attribute reduced stamina to ageing or poor fitness. Weight loss, frailty and loss of independence can become prominent. A progressive change from previous function deserves assessment. Pulmonary hypertension Extensive fibrosis can destroy small pulmonary vessels and lower oxygen levels. Pressure can then rise within the pulmonary circulation. Pulmonary hypertension can worsen breathlessness, fatigue, chest discomfort and fainting. It may eventually strain the right side of the heart. Right heart failure Advanced pulmonary hypertension can cause right heart failure. Possible features include ankle swelling, abdominal fullness and raised neck veins. These signs have several possible causes and require cardiac and respiratory assessment. Acute exacerbation of pulmonary fibrosis An acute exacerbation is a sudden clinically important worsening over days or weeks with new widespread lung opacities. It is best recognised in IPF but can occur with other fibrotic ILDs. Infection, pulmonary embolism, heart failure and aspiration must be considered. Severe acute deterioration is a medical emergency. Restrictive lung physiology Fibrotic lungs commonly have reduced capacity because they cannot expand normally. This pattern is called restriction. Forced vital capacity and total lung capacity can be reduced. The proportion exhaled in the first second is often preserved or increased relative to the total forced volume. Obstructive lung physiology Obstruction means difficulty moving air out quickly because airways are narrowed or collapse during expiration. Asthma and COPD are important obstructive diseases. The FEV1 to FVC ratio is commonly reduced. Air trapping can increase some lung volumes rather than reducing them. Restriction and obstruction are not diagnoses A lung function pattern describes physiology rather than the exact disease. Obesity, muscle weakness and chest wall disease can produce restriction without lung fibrosis. Pulmonary fibrosis can occasionally coexist with emphysema or airway obstruction. Tests must be interpreted with imaging and the symptoms and background. Bronchiectasis is not always obstructive Bronchiectasis is structural airway widening rather than one fixed spirometry pattern. It often produces airflow obstruction but can show normal, mixed or restrictive results. Pulmonary fibrosis mainly affects the gas exchange tissue and lung compliance. A person can have both bronchiectasis and fibrotic ILD. Spirometry Spirometry measures how much air is exhaled and how quickly it leaves the lungs. FVC is the total forced volume exhaled after a full breath in. FEV1 is the volume exhaled during the first second. Spirometry supports assessment but cannot confirm pulmonary fibrosis. Full lung volume testing Total lung capacity measures the amount of air within the lungs after a full inspiration. A reduced total lung capacity confirms physiological restriction. Spirometry alone can suggest restriction but cannot prove that total capacity is reduced. Gas transfer testing Gas transfer testing is commonly called TLCO or DLCO. It estimates how effectively gas moves from the air sacs into blood. Fibrosis commonly reduces this measurement by thickening and reducing the gas exchange surface. Anaemia, emphysema and pulmonary vascular disease can also lower it. Exercise testing A six minute walk test measures functional exercise capacity. Oxygen saturation and symptoms are recorded before and during walking. The result can guide rehabilitation and oxygen assessment. One walking distance should not be used alone to predict an individual's prognosis. Initial assessment The clinician asks about symptom duration, smoking and health problems in the family. They take a detailed occupational, environmental and medicine details. They ask about birds, mould, hot tubs, farming, hobbies and home water damage. They also look for autoimmune symptoms and previous radiotherapy or severe lung injury. Chest X ray A chest X ray can show reticular shadowing, reduced lung volumes or another cause of symptoms. Early fibrotic disease can be missed or appear non specific. The X ray cannot reliably classify the ILD pattern. A normal result does not exclude clinically important early disease. High resolution CT High resolution CT is usually shortened to HRCT. It uses thin image sections and reconstruction methods to show lung architecture in detail. It is the key imaging investigation for suspected fibrotic ILD. The scan identifies the distribution and pattern of reticulation, traction change, honeycombing and ground glass opacity. Reticulation Reticulation is a network of fine or coarse lines on CT. It can reflect thickened or fibrotic interstitial tissue. The location and accompanying features help determine the likely pattern. Reticulation alone does not diagnose IPF. Traction bronchiectasis Fibrotic tissue can pull airways open and distort their course. This CT feature is called traction bronchiectasis or traction bronchiolectasis. It differs mechanistically from infection driven bronchiectasis, although both involve widened airways. The surrounding fibrotic pattern helps explain the cause. Honeycombing Honeycombing describes stacked cystic air spaces, usually near the outer lung surface. It reflects established architectural destruction and fibrosis. Other cystic lung diseases can resemble honeycombing, so expert radiological interpretation matters. Usual interstitial pneumonia pattern The characteristic pathological and radiological pattern associated with IPF is called usual interstitial pneumonia, shortened to UIP. Typical CT features are mainly subpleural and basal reticulation with honeycombing and traction change. Features strongly suggesting another diagnosis reduce confidence in UIP. UIP can also occur with autoimmune disease, exposure related ILD and some medicines. IPF requires more than a UIP image A UIP pattern on HRCT is powerful diagnostic evidence. However, IPF means UIP without an identified cause. The team must still review exposure, autoimmune and medicine related possibilities. The diagnosis is an integrated specialist conclusion rather than a radiology label alone. Ground glass opacity Ground glass opacity means increased CT density through which vessels remain visible. It can reflect inflammation, partial air space filling, fine fibrosis or several other processes. A large amount of ground glass change can suggest an alternative diagnosis or acute complication. The term does not mean that the lung has turned into glass. Blood tests Blood tests help identify autoimmune disease and alternative causes. They can assess anaemia, liver function and kidney function before treatment. No blood test confirms IPF. Autoantibody results must be interpreted with the clinical pattern. Bronchoalveolar lavage Bronchoalveolar lavage involves passing sterile fluid through a bronchoscope into a small lung region and collecting it again. The returned cells and microorganisms can support or weaken particular diagnoses. It is useful in selected uncertain cases, including possible hypersensitivity pneumonitis or infection. It does not directly measure the total amount of fibrosis. Lung biopsy A lung biopsy provides tissue for microscopic assessment. Surgical biopsy can provide larger samples but carries bleeding, air leak and exacerbation risks. Transbronchial cryobiopsy is available in selected specialist centres. Biopsy is considered only when the likely diagnostic gain justifies the risk. Many people do not need a biopsy A confident diagnosis may be possible from what the person describes, lung function and HRCT pattern. Biopsy is not performed simply to prove that visible fibrosis exists. Older age, severe disease and other health problems can increase procedural risk. Uncertainty can sometimes be managed through specialist follow up rather than unsafe testing. Multidisciplinary team diagnosis NICE requires IPF diagnosis by consensus within an ILD multidisciplinary team. The discussion brings together respiratory, radiology and pathology expertise. Specialist nurses and other professionals contribute to the pathway. The team compares the history, imaging, physiology and tissue findings when available. Why multidisciplinary discussion matters Fibrotic ILDs often overlap in symptoms and CT appearance. A radiological pattern can have several causes. A positive antibody can be incidental, and an exposure can occur without disease. Combining evidence reduces false certainty and helps select safer treatment. Monitoring progression Serial lung function tests show whether FVC or gas transfer is declining. Symptoms, oxygen levels, exercise capacity and imaging can provide additional evidence. A small change in one test may reflect effort or measurement variability. Clinicians look for a consistent trend rather than reacting to one isolated number. FVC does not measure the whole illness Forced vital capacity is important for monitoring and treatment eligibility. It does not directly measure breathlessness, oxygen transfer, pulmonary hypertension or quality of life. A person can have significant symptoms despite a relatively preserved FVC. Treatment depends on the diagnosis The treatment plan first asks whether the fibrosis is IPF or has an identifiable cause. It then considers whether inflammation remains active and whether fibrosis is progressing. Supportive care, rehabilitation and symptom treatment are important across several diagnoses. Disease modifying medicines differ between conditions. Antifibrotic medicines Antifibrotic medicines slow pathways involved in progressive fibrosis. They do not remove established scar tissue or return the lungs to normal. The two established antifibrotics for IPF are nintedanib and pirfenidone. Specialist teams assess eligibility, contraindications, preferences and monitoring requirements. Nintedanib Nintedanib blocks several intracellular signalling pathways involved in fibroblast activity and blood vessel growth. NICE recommends it as an option for eligible adults with IPF across specified FVC ranges. It is also recommended for selected progressive fibrosing ILDs other than IPF. Common adverse effects include diarrhoea, nausea, reduced appetite and weight loss. Pirfenidone Pirfenidone has antifibrotic and anti inflammatory effects that slow decline in some people with IPF. NICE recommends it for eligible adults within its specified FVC criteria. Possible adverse effects include nausea, indigestion, fatigue and photosensitive rash. Liver blood tests and sun protection advice form part of safe treatment. Antifibrotics slow rather than cure A person can continue to experience progression while taking an antifibrotic. The expected benefit is a slower average decline than without treatment. Some people stop or change treatment because of adverse effects or lack of ongoing eligibility. The treatment response cannot be judged from symptoms alone over a few days. Immunosuppression is not routine IPF treatment Prednisolone, azathioprine and several older immune treatments do not provide routine disease modifying treatment for IPF. Some combinations have caused harm. This differs from certain autoimmune or inflammatory ILDs where immunosuppression can be appropriate. The exact diagnosis must therefore precede treatment assumptions. Treating connective tissue disease associated ILD Treatment targets the underlying autoimmune process and the lung behaviour. Options can include corticosteroids or other immunomodulatory medicines in selected conditions. Nintedanib can be appropriate for some progressive fibrosing ILDs. Respiratory and rheumatology specialists balance lung benefit against infection and medicine risks. Treating hypersensitivity pneumonitis Identifying and reducing exposure to the responsible antigen is central when possible. This can involve workplace controls, removal of mould or changes involving birds and feather products. Exposure removal should be evidence led because unnecessary major life changes can cause harm. Anti inflammatory or antifibrotic treatment is considered according to the disease pattern and progression. Treating occupational disease Further harmful exposure should be reduced or stopped through specialist occupational advice. The person may need workplace assessment, respiratory protection and legal or compensation information. Established fibrosis can progress despite exposure ending, so follow up remains necessary. Treating drug induced disease The suspected medicine is reviewed with the responsible specialist. Stopping the drug can prevent further injury, but recovery depends on the pattern and extent of damage. Some inflammatory reactions improve with corticosteroids, while fixed fibrosis may persist. The medicine should be recorded clearly to prevent unsafe re exposure when appropriate. Pulmonary rehabilitation NICE recommends assessing people with IPF for pulmonary rehabilitation at diagnosis. The programme combines exercise, education and strategies for managing breathlessness. It can improve exercise capacity, confidence and quality of life. The training is adapted to oxygen needs, frailty and other health conditions. Exercise Regular activity helps maintain muscle strength and daily function. The exercise plan should account for exertional oxygen desaturation and symptom severity. A person should not be told simply to push through severe breathlessness. Pulmonary rehabilitation provides a safer structured approach. Oxygen therapy Oxygen treats low blood oxygen rather than fibrosis itself. Long term oxygen can be prescribed when formal assessment shows chronic hypoxaemia. Ambulatory oxygen can be considered when oxygen falls during activity and treatment improves function or symptoms. Oxygen should be prescribed with a flow rate and use plan rather than bought casually. Pulse oximetry limitations Pulse oximeters estimate oxygen saturation through light absorption. Movement, cold hands, nail products and poor circulation can reduce accuracy. Some devices can overestimate oxygen saturation in people with darker skin. Symptoms and repeated clinical measurements matter when a reading is borderline or unexpected. Vaccination and infection prevention Influenza, pneumococcal and other nationally recommended vaccinations reduce some preventable respiratory risks. Smoking cessation prevents additional lung and cardiovascular harm. Prompt assessment is important when infection causes a marked change from stable symptoms. Vaccination cannot prevent every acute deterioration. Treating cough and breathlessness Clinicians assess reflux, upper airway disease, infection and other treatable contributors to cough. Low dose opioid treatment can help selected people with severe refractory breathlessness or cough. Palliative care teams support symptom control alongside active antifibrotic and transplant pathways. Palliative care does not mean that disease directed treatment has stopped. Nutrition and weight Breathlessness, cough and medicine adverse effects can reduce appetite. Unintended weight loss and muscle loss can reduce strength and transplant eligibility. Dietetic support can help maintain adequate nutrition. Obesity can also worsen breathlessness and complicate transplant assessment. Lung transplantation Lung transplantation replaces one or both diseased lungs with donor lungs. It is the only treatment capable of replacing extensively fibrotic lung tissue. It is suitable only for selected people because donor organs are limited and major risks remain. NICE advises discussing transplantation within months of IPF diagnosis when no absolute contraindication exists. Transplant assessment The transplant centre assesses disease severity, rate of progression and expected survival without transplantation. It also considers age, frailty, other organ function, infection, cancer risk and social support. Early referral creates time for assessment before the person becomes too unwell. Referral does not guarantee listing or transplantation. Complications of advanced fibrosis Advanced disease can cause chronic respiratory failure, pulmonary hypertension and right heart strain. Chest infections and pulmonary embolism can produce additional deterioration. Pneumothorax and lung cancer risk may also be relevant in selected people. New symptoms should not be assumed to represent ordinary progression. Acute worsening needs urgent assessment Sudden breathlessness can result from infection, pulmonary embolism, pneumothorax or heart failure. It can also represent an acute exacerbation of fibrotic ILD. These causes cannot be distinguished safely from symptoms alone. Severe deterioration requires emergency hospital assessment. Follow up Specialist review includes symptoms, lung function, oxygen needs and medicine tolerance. The frequency reflects stability and rate of progression. Rehabilitation, transplant suitability, psychological needs and palliative support are revisited. The care plan should explain who to contact during deterioration. Prognosis in IPF IPF is usually progressive and can shorten life. The rate varies greatly between people and can change over time. Some people remain relatively stable for years, while others decline more rapidly or experience acute exacerbations. Antifibrotics and supportive care can slow decline and improve daily life, but they do not eliminate uncertainty. Prognosis in other fibrotic ILDs The outlook depends on the cause, imaging pattern and response to exposure removal or treatment. Some conditions stabilise or improve when inflammation is controlled. Others develop progressive pulmonary fibrosis despite appropriate care. Population statistics cannot predict one person's exact course. Discussing prognosis honestly People differ in how much prognostic detail they want and when they want it. Clinicians should explain the known range without presenting one average as a deadline. Planning can include work, travel, oxygen, transplant assessment and future care preferences. Hope can focus on symptom control, relationships, function and access to evolving treatments. Emotional and practical effects Progressive breathlessness can alter employment, family roles and independence. Fear of exertion and acute deterioration can cause anxiety. Cough can be socially isolating and disturb sleep. Specialist nurses, rehabilitation, psychology, welfare advice and patient support organisations can help. What this lesson should not be used for This lesson cannot diagnose IPF from breathlessness, crackles, clubbing or one CT phrase. It cannot determine whether fibrosis is idiopathic, autoimmune, exposure related or medicine induced without specialist assessment. Do not stop an important medicine or remove a major environmental exposure solely from general educational information. Do not start oxygen, corticosteroids or antifibrotic treatment without a specialist plan. Call 999 for severe breathing difficulty, blue or grey colour, collapse or rapidly reduced consciousness.

Pulmonary fibrosis is persistent scarring within the lung's gas exchange tissue. IPF is the archetypal progressive form without an identified cause, while other fibrotic ILDs can result from exposure, autoimmune disease, hypersensitivity or medicines. HRCT, lung function and specialist multidisciplinary discussion establish the diagnosis and guide cause specific or antifibrotic treatment.