Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease where the immune system mistakenly attacks its own healthy tissues, leading to widespread inflammation and organ damage. Because SLE is systemic, it can affect virtually any organ, from the skin and joints to the kidneys and brain. The lungs are a frequent target, with estimates suggesting that 50% to 70% of individuals with SLE will experience some form of lung involvement. These pulmonary complications arise from inflammation directed at the protective linings, the lung tissue itself, or the blood vessels within the lungs, ranging from mild issues to severe, life-threatening conditions.
Pleurisy and Pleural Effusions
Pleurisy, the inflammation of the pleura, is the most common respiratory manifestation in lupus patients. The pleura is the two-layered membrane surrounding the lungs and lining the chest cavity. When inflamed due to lupus activity, the normally smooth surfaces become rough and rub against each other during respiration.
The primary symptom is a sharp, stabbing chest pain, which is exacerbated when the person takes a deep breath, coughs, sneezes, or laughs. This pain is reported by 45% to 60% of people with SLE. Inflammation can also cause fluid to leak into the space between the pleural layers, a complication known as a pleural effusion.
Pleural effusions occur in a significant number of patients, sometimes affecting up to 60%, though they are often small and asymptomatic. Larger fluid accumulations press on the lung, causing shortness of breath and a dry cough. These effusions are typically exudative, meaning they are rich in protein and inflammatory cells, and frequently affect both lungs.
Acute Lupus Pneumonitis
Acute lupus pneumonitis is a direct, rapid-onset inflammation of the lung parenchyma. This severe condition targets the alveolar structures rather than the outer lining, distinguishing it from pleurisy. Although serious, it is less common, affecting an estimated 1% to 10% of lupus patients.
The onset is typically severe, presenting with high fever and pronounced shortness of breath. Patients also frequently experience chest pain and hemoptysis (coughing up blood). Since these symptoms can mimic a severe infection, aggressive diagnosis is required to differentiate the autoimmune flare from a microbial cause.
Due to the rapid progression and potential for respiratory failure, this condition requires immediate and aggressive treatment. Treatment typically involves high-dose systemic corticosteroids along with other immunosuppressive agents. Even with prompt care, the underlying acute alveolar injury can sometimes lead to permanent scarring of the lung tissue.
Interstitial Lung Disease
In contrast to acute pneumonitis, lupus-related interstitial lung disease (ILD) is a chronic condition that develops slowly. ILD involves persistent inflammation and subsequent scarring, or fibrosis, of the lung’s delicate interstitium. This fibrosis causes the lungs to become stiff and less elastic, reducing their ability to expand and transfer oxygen into the bloodstream.
The slow accumulation of damage means that ILD symptoms, such as progressive shortness of breath and a persistent dry cough, develop gradually. This reduced gas exchange capacity is commonly measured by a decrease in the diffusing capacity of the lungs for carbon monoxide (DLCO) on pulmonary function tests. Affecting approximately 3% to 9% of SLE patients, the resulting damage is often irreversible.
Management of ILD focuses on halting the inflammatory process and preventing further scarring of the lung tissue. Initial treatment often involves systemic glucocorticoids and various immunosuppressive drugs to control the underlying autoimmune activity. For progressive fibrosing phenotypes, newer antifibrotic medications may be used to slow the rate of decline in lung function.
Pulmonary Vascular and Mechanical Complications
Lupus can affect the lung’s circulatory system and the mechanics of breathing, leading to unique and serious complications. Pulmonary Hypertension (PH) involves high blood pressure in the arteries that supply the lungs. Persistent inflammation and damage in SLE can lead to remodeling and thickening of these small pulmonary arteries, forcing the heart’s right side to work harder to pump blood.
The increased risk for Pulmonary Emboli (PE) involves blood clots that travel to and lodge in the lung arteries. People with lupus often have a higher risk of developing clots due to antiphospholipid antibodies, which promote a hypercoagulable state. Symptoms of a PE include sudden chest pain, unexplained shortness of breath, and a rapid heart rate, requiring emergency anticoagulant therapy.
Shrinking Lung Syndrome (SLS) is a unique complication that is mechanical rather than inflammatory. SLS is believed to be caused by weakness or dysfunction of the diaphragm muscle, which reduces the volume of the lungs. Patients present with progressive dyspnea and pleuritic chest pain. Chest imaging typically shows elevated diaphragms and reduced lung volumes without significant fibrosis.