Interstitial lung disease: symptoms, causes, diagnosis and treatment

ILD often starts slowly. Asthma + Lung UK says common symptoms such as breathlessness, persistent cough and tiredness are non-specific and may be mistaken for asthma or COPD, or put down to ageing or lack of fitness, which is one reason ILD can be overlooked in primary care.

It lists the signs and symptoms below. The NHS description of idiopathic pulmonary fibrosis, the best-known ILD, is similar: shortness of breath, a dry cough that does not go away, tiredness and clubbing, with symptoms that usually start slowly and continue to get worse over time.

• Gradual breathlessness that is worse on exertion (Asthma + Lung UK).

• A persistent daily cough lasting more than 8 weeks, often but not always dry (Asthma + Lung UK).

• Fatigue (Asthma + Lung UK, NHS).

• Unintentional weight loss (Asthma + Lung UK).

• Clubbing of the fingers: fingernails curving over rounded fingertips (Asthma + Lung UK, NHS).

• Crackling sounds ("velcro" crackles) at the bases of the lungs when a clinician listens with a stethoscope (Asthma + Lung UK).

Asthma + Lung UK describes interstitial lung diseases as a group of over 200 diseases that cause scarring (fibrosis) or inflammation in the lung parenchyma, the part of the lungs involved in gas exchange. Some cause the lung tissue to become stiff, thickened or scarred, which is known as pulmonary fibrosis.

Fibrotic ILDs are restrictive lung diseases because scarring reduces lung volume and limits how fully the lungs expand. This differs from obstructive diseases such as asthma and COPD, in which narrowed airways make it hard to breathe out. It is possible to have both.

Not all ILDs lead to permanent scarring. Some are mainly inflammatory and may respond well to treatment, and prompt diagnosis and management can help control inflammation, improve symptoms and in some cases reduce the risk of progression to irreversible lung damage, according to Asthma + Lung UK.

Asthma + Lung UK says that for many people with an ILD there is no clearly identifiable cause, which is called idiopathic ILD. It lists groups at higher risk based on age, medical history, environmental exposure and lifestyle.

• Older age, especially for idiopathic pulmonary fibrosis (Asthma + Lung UK).

• Connective tissue diseases such as rheumatoid arthritis, systemic sclerosis and lupus (Asthma + Lung UK).

• Smoking or having smoked (Asthma + Lung UK).

• Long-term exposure to inhaled dusts and allergens such as asbestos, silica, coal dust, mould and bird proteins (Asthma + Lung UK). The NHS also links IPF in some cases to long-term exposure to metal, wood or asbestos dust.

• Medicines including the chemotherapy drug bleomycin, the heart rhythm drug amiodarone and the antibiotic nitrofurantoin (Asthma + Lung UK).

• A family history of ILD, particularly IPF (Asthma + Lung UK, NHS).

• Gastro-oesophageal reflux disease (GORD), which is common in IPF; Asthma + Lung UK says microaspiration of stomach contents may contribute to lung damage.

Asthma + Lung UK says diagnosis usually takes place in secondary care and is often made by a multidisciplinary team. A GP will usually start by asking about symptoms, exposures such as work and birds or mould, medicines and family history, and listening to the chest.

The NHS description for IPF says a doctor who thinks you may have it will refer you to a specialist in hospital for tests, including a spirometry test (a breathing test to check how well your lungs work) and a chest X-ray followed by a chest CT scan to look for scarring. If the cause is still not clear, a bronchoscopy or lung biopsy may be offered.

The specialist team combines clinical, scan and sometimes biopsy results to reach the most likely diagnosis, because treatment differs between the types of ILD.

Asthma + Lung UK says medicines for ILD are limited and can carry a high burden of side effects, and that most are started and monitored by specialist teams. They fall into two broad groups: antifibrotics to slow the development of scarring, and immunosuppressants to target inflammation that is potentially reversible.

Two antifibrotics are available: nintedanib, whose most common side effect is diarrhoea, and pirfenidone, which can cause stomach symptoms and photosensitivity, so direct sunlight is avoided and SPF 50 sunscreen is advised year round. Asthma + Lung UK says these slow progression but do not stop scarring entirely or reverse existing scar tissue. The NHS says people taking them need regular blood tests.

Immunosuppressant medicines such as prednisolone, mycophenolate, azathioprine, methotrexate, cyclophosphamide, rituximab or tocilizumab are used where inflammation plays a significant role, for example in hypersensitivity pneumonitis, sarcoidosis and autoimmune ILD.

Supportive treatment matters too. Pulmonary rehabilitation is recommended for people with ILD who are limited by breathlessness, and Asthma + Lung UK says home oxygen assessment is advised if saturations are 92% or below or there is significant desaturation on exertion. The NHS also lists stopping smoking, exercising, a healthy balanced diet, and annual flu, pneumococcal and RSV vaccines if eligible.

For a small number of people whose fibrosis progresses despite treatment, lung transplantation may be considered. Asthma + Lung UK says it is relatively uncommon, with 135 adult lung transplants in the UK in 2023 to 2024 (not all for pulmonary fibrosis).

Asthma + Lung UK says cough is common and often distressing, typically dry and persistent, and that more frequent and severe cough has been associated with disease progression and poorer quality of life. Many people have cough hypersensitivity, where triggers include cold air, strong smells, smoke, vaping, cleaning products, perfumes and dust.

There are no licensed treatments specifically for ILD cough, but specialist teams can look for treatable contributors such as GORD, postnasal drip and infections, and respiratory physiotherapists and speech and language therapists can teach cough suppression techniques.

Asthma + Lung UK says outcomes depend on the underlying condition, severity, rate of progression and response to treatment. Some people stabilise or improve, others develop permanent scarring, and progressive pulmonary fibrosis is life-limiting with no cure.

For IPF, Asthma + Lung UK says median survival after diagnosis was historically estimated at around 3 to 5 years, but those estimates predate antifibrotic therapy and many people now live longer. The NHS says that if treatment works well you may not have many symptoms for years, and that IPF can eventually lead to chest infections, pulmonary hypertension and heart failure.

The NHS says to see a GP if you think you might have IPF, if you have shortness of breath that gets worse with normal activities or when you lie down, or if you have had a cough for 3 weeks or more. Asthma + Lung UK lists chest pain, leg swelling, palpitations, coughing up blood and weight loss as symptoms to record and investigate.

For sudden severe breathlessness, call 999 or go to A&E.

On the NHS, ILD is usually diagnosed after a GP referral to a respiratory or ILD specialist team, with CT scanning and lung function tests. Antifibrotic medicines are prescribed by specialist teams. Private respiratory consultations and CT scans are available for quicker assessment, but long-term antifibrotic treatment and monitoring are generally arranged through the specialist ILD service, so make sure results are shared with your GP.