When the lungs cannot expand properly, it impacts the body’s ability to breathe effectively. Shrinking lung syndrome is a condition where the lungs appear smaller than they should, leading to breathing difficulties.
What is Shrinking Lung Syndrome?
Shrinking lung syndrome (SLS) is a condition marked by a reduction in lung volume, where the lungs appear smaller on imaging. This is often due to external factors affecting lung expansion rather than damage to the lung tissue itself. The primary characteristic involves restricted movement of the diaphragm, the muscular wall separating the chest and abdomen, or other pressures outside the lungs. The condition is also sometimes referred to as Vanishing Lung Syndrome (VLS) or Pleural Effusion-Associated Diaphragmatic Dysfunction (PEADD).
Unlike conditions that damage lung tissue, SLS involves a mechanical restriction. The lungs do not fully inflate, appearing “shrunken” on imaging. This limitation stems from the chest cavity’s inability to expand and the diaphragm’s inability to contract effectively.
Underlying Causes
Shrinking lung syndrome is most frequently associated with systemic lupus erythematosus (SLE), an autoimmune disease where the body’s immune system mistakenly attacks its own tissues. In SLE, inflammation of the pleura (the lining surrounding the lungs) and the diaphragm can occur, limiting their movement. Approximately 0.5% to 1.1% of individuals with SLE may develop SLS.
Other autoimmune conditions, such as Sjögren’s syndrome, rheumatoid arthritis, and scleroderma, have also been linked to SLS. The exact mechanisms are not fully understood, but hypotheses include inflammation of the pleura, dysfunction of the diaphragm, and issues with the phrenic nerve which controls diaphragm movement. Chronic inflammation of the pleura, for instance, can impair deep inspiration, leading to reduced lung compliance over time.
Conditions that cause fluid buildup around the lungs (pleural effusions) can also contribute to SLS by compressing the lungs and preventing full expansion. Severe obesity can mechanically restrict the diaphragm’s movement and overall lung expansion due to the weight on the chest and abdomen. This external pressure can lead to reduced lung volumes.
Identifying the Signs
The primary symptom of shrinking lung syndrome is shortness of breath, medically known as dyspnea, which often worsens with physical activity. This occurs because the restricted lung volume means less air can be taken in with each breath, requiring more effort to breathe. Chest pain is another common indicator, frequently described as pleuritic, meaning it is sharp and often intensifies with deep breaths. This pain arises from inflammation of the pleural lining.
Individuals may also experience a cough, which is typically dry and results from the irritation caused by reduced lung movement or inflammation. Reduced exercise tolerance is a frequent complaint, as the body struggles to meet its oxygen demands during activity due to the limited lung capacity. These symptoms directly reflect the mechanical limitations imposed on the respiratory system, making it harder for the lungs to perform their function efficiently.
Diagnosis and Management
Diagnosing shrinking lung syndrome involves a comprehensive evaluation, as it is often a diagnosis of exclusion. A medical history, focusing on autoimmune conditions and respiratory symptoms, is followed by a physical examination. Pulmonary function tests (PFTs) are crucial, typically showing reduced lung volumes, such as total lung capacity and vital capacity, indicating a restrictive pattern without significant airway obstruction. Imaging studies like chest X-rays and CT scans often reveal elevated diaphragms and smaller lung volumes, but generally no significant damage to the lung tissue itself.
The diagnosis also involves ruling out other conditions that can cause similar symptoms or restrictive lung patterns, such as pulmonary fibrosis, large pleural effusions, or neuromuscular disorders. Diaphragmatic ultrasound can also be used to visualize and confirm diaphragm dysfunction. Blood tests may be conducted to check for markers of inflammation or specific autoimmune antibodies, especially if an underlying autoimmune disease is suspected.
Management of shrinking lung syndrome primarily focuses on treating the underlying cause, especially if it’s an autoimmune disease like SLE. Corticosteroids are frequently used as a first-line treatment to reduce inflammation, with initial doses often ranging from 0.5 to 1 mg/kg of prednisolone daily. In cases that do not respond to initial treatment, other immunosuppressive medications, such as rituximab or cyclophosphamide, may be considered. Supportive care measures aim to improve lung function and manage symptoms. These can include physical therapy and respiratory exercises to enhance chest wall mobility and strengthen the diaphragm.