Sjögren’s syndrome (SS) is a systemic autoimmune disorder where the immune system mistakenly attacks healthy tissues, primarily targeting the moisture-producing exocrine glands. However, Sjögren’s is not limited to these glands and can affect many non-glandular areas throughout the body, including the skin, joints, kidneys, and nervous system. The involvement of the lungs, which occurs in a significant percentage of patients, can lead to serious respiratory complications and is a major concern for long-term health. This article explores the specific mechanisms by which Sjögren’s syndrome impacts the respiratory system and the resulting conditions.
The Underlying Cause of Lung Damage
The damage to the lung tissue is fundamentally driven by the same misguided immune process that affects the salivary and lacrimal glands. This process involves the chronic infiltration of immune cells, specifically lymphocytes, into the lung’s parenchyma (tissue) and airways. These white blood cells gather around the small airways and in the tissue between the air sacs, causing a persistent state of inflammation.
A related mechanism of lung complication stems from the sicca symptoms affecting the respiratory tract itself, a condition sometimes called xerotrachea. The exocrine glands lining the airways normally produce mucus and fluid, and their destruction impairs the mucociliary clearance system. This system, which uses tiny, hair-like cilia to sweep foreign particles and pathogens out of the lungs, becomes less effective due to the dryness and lack of proper lubrication. The resulting chronic irritation and accumulation of debris can lead to persistent cough and increase the risk of recurrent respiratory infections.
Types of Pulmonary Disease Linked to Sjögren’s
Interstitial Lung Disease (ILD)
Interstitial Lung Disease is characterized by inflammation and scarring (fibrosis) of the tissue surrounding the air sacs in the lungs. This scarring makes the lungs stiff, impairing their ability to take in oxygen and leading to breathlessness. Non-specific interstitial pneumonia (NSIP) is the most frequently identified pattern of ILD associated with Sjögren’s, often presenting with a mix of inflammation and fibrosis.
The NSIP pattern typically shows ground-glass opacities and reticular abnormalities on imaging, often sparing the subpleural areas of the lung. Usual interstitial pneumonia (UIP), another subtype, is less common but carries a worse prognosis due to its characteristic pattern of dense, destructive fibrosis and honeycombing. Lymphocytic interstitial pneumonia (LIP) is another pattern strongly associated with Sjögren’s, characterized by a dense infiltration of lymphocytes and plasma cells that can eventually form cysts within the lung tissue.
Airway Disease (Bronchitis/Bronchiolitis)
Airway disease is an extremely common manifestation of Sjögren’s, often occurring more frequently than ILD, though it is usually less life-threatening. This condition involves the inflammation and damage to the small airways, known as bronchiolitis, which can lead to obstruction of airflow. Follicular bronchiolitis is a specific type resulting from the accumulation of lymphoid cells around the bronchioles, which can cause cysts in the lungs.
Chronic inflammation and infection can also lead to bronchiectasis, a condition where the airways become permanently widened and damaged. Bronchiectasis makes it difficult to clear mucus and increases the risk of recurrent respiratory infections. Patients with small airway disease may experience a chronic, dry, often debilitating cough and wheezing that is sometimes mistaken for asthma. While airway disease typically does not affect respiratory function as severely as ILD, it significantly impacts the patient’s quality of life.
Pleural Disease
Inflammation can occasionally affect the pleura, which is the double-layered membrane that lines the outside of the lungs and the inside of the chest cavity. This inflammation, known as pleuritis, can be accompanied by a buildup of fluid in the space between the layers, called a pleural effusion. Pleural involvement is a less frequent occurrence than ILD or airway disease in Sjögren’s syndrome. When it does occur, it should prompt a thorough investigation to rule out other co-existing autoimmune conditions or infections.
Identifying Lung Involvement
The first indications of Sjögren’s-related lung involvement are often subtle and can be easily overlooked or attributed to other causes. Common symptoms include a persistent dry cough that is not resolved by standard treatments and shortness of breath, particularly during physical activity (exertional dyspnea). Patients may also report significant fatigue and a higher-than-normal frequency of respiratory infections, which are often a sign of underlying bronchiectasis.
Because symptoms can be vague, medical confirmation relies on specialized diagnostic tools. Pulmonary Function Tests (PFTs) are used to measure how well the lungs are working, revealing restrictive patterns (suggesting ILD) or obstructive patterns (suggesting airway disease). The most sensitive and specific imaging tool is a High-Resolution Computed Tomography (HRCT) scan, which provides detailed pictures of the lung structure. The HRCT scan is the standard method for visualizing and characterizing the extent of interstitial changes, such as ground-glass opacities and honeycombing, or the presence of bronchiectasis in the airways.
Management of Sjögren’s Related Lung Conditions
Treatment strategies depend heavily on the specific type and severity of lung involvement, particularly whether the condition is primarily inflammatory or fibrotic (scarred). For conditions where inflammation is the dominant feature, such as cellular NSIP or Lymphocytic Interstitial Pneumonia, the primary approach involves immunosuppressive therapy. Corticosteroids, such as prednisone, are often used to rapidly reduce acute inflammation in the lungs.
Steroid-sparing agents like mycophenolate mofetil or azathioprine are frequently used for long-term control of the underlying systemic inflammation in patients with more severe ILD. For certain cases that do not respond to initial therapies, biological agents like rituximab, which targets B-cells, may be considered to modulate the autoimmune response. Management also includes supportive care measures, such as supplemental oxygen for patients with low blood oxygen levels and pulmonary rehabilitation to improve lung function and quality of life. Patients with bronchiectasis benefit from treatments aimed at clearing mucus and managing recurrent infections, often requiring close collaboration between a rheumatologist, who manages the autoimmune disease, and a pulmonologist, who manages the lung condition.