Can Rheumatoid Arthritis Affect the Lungs?

Rheumatoid arthritis can affect the lungs because it's a systemic disease, which means it can affect any organ. However, its predominant involvement is in the joints.

Written and verified by the doctor Leonardo Biolatto.

Last update: 06 October, 2022

Rheumatoid arthritis is an inflammatory disease that usually affects the joints and is suffered by 1% of the world’s population. However, rheumatoid arthritis can also affect the lungs directly and indirectly.

Up to 50% of patients with rheumatoid arthritis show extra-articular disturbances, such as disturbances in the heart, lungs, kidneys, blood and even the nervous system.

In this article, we’ll explain how rheumatoid arthritis can affect the lungs, the symptoms it produces, and its treatment.

What is rheumatoid arthritis?

Rheumatoid arthritis is a chronic inflammatory autoimmune disease. It tends to occur at any age, but is more common in middle age, between 40-50 years, and in women.

It’s an autoimmune disease because our body loses tolerance to our own tissues and attacks them as if they were foreign, causing them to deteriorate. This technically translates into the appearance of autoantigens -our tissues- which are attacked by autoantibodies -defenses that attack our own cells.

Although it can affect any organ, rheumatoid arthritis predominantly affects the joints, specifically their synovial membrane. This is a layer that envelops the joint and nourishes it, as there are no blood vessels inside the joint to provide nutrients.

Due to the attack on our immune system, the synovial membrane becomes chronically inflamed and destroys the joint cartilage. If left untreated, it can lead to bone destruction.

Can rheumatoid arthritis affect the lungs?

Rheumatoid arthritis can affect any structure that makes up the lung: the pleura, airways, blood vessels, respiratory muscles, and the lung itself.

The process by which lung involvement occurs is unknown. However, it has been observed that several factors may be involved such as:

• The person’s genetic predisposition.
• Immunological alterations that occur in the body.
• Environmental factors, such as smoking. For example, men between 50-70 years old with more active rheumatoid arthritis and a history of smoking are more likely to develop lung problems.

Pulmonary involvement by rheumatoid arthritis can occur in a variety of ways, as we will see below.

Interstitial lung disease, or ILD

The most common form of presentation of rheumatoid arthritis (RA) in the lung is interstitial lung disease (ILD). It’s estimated that in patients with RA, up to 58% may have ILD.

The lung in a healthy person is elastic to allow for expansion each time the person inhales air. However, in ILD, the lung becomes inflamed and fibrotic, causing a loss of elasticity. This makes it unable to expand properly and the patient can’t breathe well.

In addition, ILD can damage nearby structures, such as airways and blood vessels, further worsening the patient’s symptoms of choking.

Pulmonary hypertension

This entity is more common than expected and occurs in 30% of patients with RA. It’s usually asymptomatic and is a consequence of the progression of ILD.

Under normal conditions, the right side of the heart pumps blood through the lungs, where it picks up oxygen. The blood then returns to the left side of the heart, from where it is directed to the rest of the body.

Because of ILD, the lung becomes increasingly stiff, causing the pulmonary vessels to become occluded and unable to carry much blood. When this happens, pressure builds up causing pulmonary hypertension.

RA treatment-induced lung disease

Many of the drugs used in RA are associated with lung injury as an adverse effect. This adverse effect is especially seen in the use of methotrexate which is an immunomodulator and anti-inflammatory. These drugs cause fibrosis of the lungs.

Pleural disease

The pleura are two layers that envelop the lung and separate it from other tissues. Pleural involvement is a frequent manifestation of lung disease in RA. According to a study on RA and its relationship with the lung carried out in 2008:

This involvement causes the pleura to fill with fluid continuously and it has to be drained; that is, a tube connecting the outside with the pleura has to be placed to remove the fluid.

Rheumatoid nodules

Small lumps may form in the lungs known as pulmonary rheumatoid nodules. Lung nodules usually have no signs or symptoms and don’t pose a risk of lung cancer.

However, in some cases, cavities can develop within a nodule, which can become over-infected and create communication with other tissues, spreading infection.

Airways

The air passages through which air enters and exits, i.e. bronchi, bronchioles, and alveolar sacs, can be affected. The immune system continually attacks them, causing them to thicken and become obstructed, blocking the passage of air.

Diagnosis and treatment of RA lung disease

If you have rheumatoid arthritis and have respiratory symptoms, you need to see your doctor. An example of these symptoms may be shortness of breath that cannot be explained by any other cause.

Diagnosis is based primarily on imaging tests, clinical history, respiratory function tests, and a biopsy – a small piece of lung is examined under a microscope.

Treatment of lung involvement is by continued medication for rheumatoid arthritis. However, if the pulmonary involvement is caused by this exact medication, it should be withdrawn and replaced by one that doesn’t cause pulmonary toxicity.