Interstitial lung disease (ILD)

Interstitial lung disease, or ILD, is the umbrella name for a large family of conditions that affect the interstitium, the delicate tissue that lies between the lungs' tiny air sacs and supports them. In ILD this tissue becomes inflamed and, over time, scarred. That scarring is known as fibrosis, which is why many people know the problem by the term pulmonary fibrosis. As the tissue thickens and stiffens, the lungs become less able to move oxygen into the bloodstream, and breathing takes more effort.

Pulmonary fibrosis is therefore one part of the wider picture of ILD rather than a separate condition. ILD has many causes: in some people no cause is ever found (idiopathic pulmonary fibrosis), while in others it follows exposure to certain dusts or medicines, or accompanies another illness. One of the most important groups of causes, and the reason a rheumatologist may be involved, is the connective tissue diseases.

Several rheumatic conditions are driven by an overactive immune system, and the same process that inflames the joints or skin can inflame and scar the lungs. This is why breathlessness and cough are taken as seriously as joint pain in someone with one of these conditions.

The associations a rheumatologist watches for include:

• Systemic sclerosis (scleroderma), where lung involvement is common and is the single most important reason for careful monitoring
• Rheumatoid arthritis, which can affect the lungs as well as the joints
• The inflammatory myopathies (myositis), where certain antibody patterns carry a particular risk to the lungs
• Sjögren's syndrome, which can involve the lungs in some people
• Mixed and undifferentiated connective tissue disease, where overlapping features can include the lungs
• Sarcoidosis, which often affects the lungs and can also involve the joints

Because ILD can develop quietly, before it causes obvious symptoms, part of specialist rheumatology care is to think about the lungs from the outset in the conditions where the risk is higher.

The two symptoms that matter most are:

• Breathlessness, particularly on exertion such as walking uphill or climbing stairs, that is new or getting worse
• A persistent dry cough that does not settle

Tiredness, reduced stamina and a feeling that you cannot take a deep breath can also feature. These symptoms come on gradually, so they are easy to put down to age, being out of condition or a lingering cold. In someone with a connective tissue disease this is exactly the assumption to avoid: new or worsening breathlessness, or a persistent cough, should always be looked into rather than dismissed as unfitness, because catching lung involvement early makes a real difference.

Assessment starts with a careful history and examination, including listening to the chest and checking the oxygen level in the blood with a simple fingertip sensor. Two tests are central:

• Lung function tests (breathing tests), which measure how much air the lungs hold and how well oxygen passes into the bloodstream
• High-resolution CT of the chest, a detailed scan that shows the pattern and extent of any inflammation or scarring

In conditions where the risk is higher, particularly systemic sclerosis, these tests are often arranged around the time of diagnosis to set a baseline and then repeated at intervals, so that any change is picked up early rather than waited for. Blood tests for particular antibodies help build the picture of the underlying condition. Where the joints are also involved, Dr Borukhson can use point-of-care ultrasound during the consultation to assess inflammation; you can read more on the ultrasound clinic page.

Treatment is guided by what is driving the disease and how it is behaving, and it is always shared with respiratory specialists.

Where inflammation is the main problem, as it often is in connective tissue disease-associated ILD, medicines that calm the immune system are used. Mycophenolate is a common choice, and others such as cyclophosphamide or rituximab may be considered in selected cases; a corticosteroid such as prednisolone is sometimes used, thoughtfully, alongside them. Where scarring is progressing despite treatment of the inflammation, an antifibrotic medicine such as nintedanib, which NICE recommends for progressive fibrosing ILD, may be added to slow the rate of scarring. Pirfenidone is another antifibrotic used in some forms of pulmonary fibrosis. These are specialist medicines, chosen for the individual and used under careful supervision with regular monitoring.

Alongside medicines, pulmonary rehabilitation, a supervised programme of exercise and education, helps many people stay active and breathe more comfortably, and oxygen is provided where the level in the blood is low. Stopping smoking, keeping up recommended vaccinations and treating chest infections promptly all help protect the lungs.

ILD sits at the meeting point of rheumatology and respiratory medicine, so it is best managed jointly. Dr Borukhson practises within a world-renowned tertiary centre, with ready access to consultant colleagues in respiratory medicine and the other specialties that may be involved. Where appropriate she can involve those specialists directly, and bring particularly complex cases to a multidisciplinary team meeting (MDT), where rheumatologists, respiratory physicians, radiologists and others agree the plan together. This means that decisions about screening, monitoring and treatment can be joined up and reached promptly.

Alongside your treatment, a few steady habits help protect your lungs and your general health:

• Stop smoking if you smoke. Nothing protects the lungs more, and support to stop is available through your GP.
• Keep as active as you can. Gentle, regular activity and any exercises from pulmonary rehabilitation help maintain stamina; pace yourself and build up gradually.
• Guard against chest infections. Keep up the flu, COVID-19 and pneumococcal vaccinations your team recommends, and seek advice early if you develop a chest infection.
• Attend your monitoring appointments. Breathing tests and scans over time are how change is caught early, even when you feel well.
• Look after your mood. Living with a lung condition can be worrying, and support for how you are coping is part of good care.

Many people with ILD stay stable for a long time, particularly when it is found early and monitored closely.

Because ILD can change over time, certain symptoms deserve prompt attention rather than waiting for a routine review.

Arrange a prompt, same-day review if you develop:

• Breathing that becomes noticeably worse over hours or days
• A new cough, breathlessness or chest tightness with a fever, which can mean a chest infection
• A sudden drop in how far you can walk or what you can manage

Call 999 or go to A&E for sudden severe breathlessness, severe chest pain, or coughing up blood.

A gradual change in your usual breathlessness or cough is still worth reporting to your team promptly, so that your treatment and monitoring can be adjusted. When you are unsure how urgent something is, it is always reasonable to ask.

In the rheumatic conditions that can affect the lungs, ILD often develops quietly, and the earlier it is recognised the more can be done to protect breathing and quality of life. A rheumatologist who thinks about the lungs from the start, arranges the right screening, and works hand in hand with respiratory colleagues gives you the best chance of staying well. If you have a connective tissue disease and have noticed new breathlessness or a persistent cough, it is worth raising it promptly rather than waiting.

Why would a rheumatologist talk to me about my lungs?

Several rheumatic conditions, above all systemic sclerosis, can involve the lungs as well as the joints and skin. The same immune process that inflames the joints can inflame and scar the lung tissue, a problem called interstitial lung disease or pulmonary fibrosis. Because this can develop quietly, a rheumatologist keeps an eye on your breathing, arranges screening where the risk is higher, and works closely with respiratory colleagues so that any lung involvement is picked up and treated early.

Is interstitial lung disease the same as pulmonary fibrosis?

They overlap. Interstitial lung disease (ILD) is the umbrella term for a large family of conditions that inflame and scar the tissue between the lungs' air sacs. Pulmonary fibrosis is the scarring itself, and it is the word many people know. So pulmonary fibrosis is one part of ILD rather than a completely separate thing. When ILD occurs alongside a rheumatic condition, it is often called connective tissue disease-associated ILD.

How is interstitial lung disease found and monitored?

The two central tests are breathing tests (lung function tests), which measure how well the lungs take in and transfer oxygen, and a detailed scan called a high-resolution CT, which shows the pattern of any inflammation or scarring. Listening to the chest and checking the oxygen level are part of the examination too. In higher-risk conditions such as systemic sclerosis, screening is often arranged at diagnosis and then repeated over time, so that any change is caught early.

How is interstitial lung disease treated?

Treatment depends on what is driving it. Where inflammation is prominent, medicines that calm the immune system, such as mycophenolate, are often used. Where scarring is progressing despite this, an antifibrotic medicine such as nintedanib may be added to slow it down. Oxygen and pulmonary rehabilitation help some people breathe and stay active more comfortably. Care is usually shared with a respiratory team, and the plan is tailored to you and reviewed over time.

When should I seek urgent help?

Seek same-day medical advice if your breathing becomes markedly worse over hours or days, or if a cough, breathlessness or chest tightness comes on with a fever, as a chest infection or a flare of lung inflammation needs prompt attention. Call 999 for sudden severe breathlessness or chest pain. A gradual change in your usual breathlessness or cough is still worth reporting to your team promptly rather than waiting for your next routine appointment.