What Causes Pleurisy and How It Affects Your Lungs
Pleurisy, also known as pleuritis, is one of the most common conditions affecting the pleura—the delicate membranes surrounding the lungs and lining the chest cavity. To fully understand pleurisy, it's essential to first grasp the anatomy of the pleura. This double-layered membrane consists of the visceral pleura, which wraps directly around the lungs, and the parietal pleura, which lines the inner chest wall. These layers work together to reduce friction during breathing and help maintain proper lung function.
Understanding the Root Causes of Pleurisy
The development of pleurisy typically stems from inflammation of the pleural tissues, often triggered by a range of underlying health issues. While the condition itself involves swelling and irritation of the pleural layers, the causes can vary significantly—from infections to more serious systemic diseases.
Bacterial and Infectious Triggers
One of the most frequent causes of pleurisy is bacterial infection. When bacteria invade the pleural space, they can cause a painful inflammatory response. A particularly notable form is tuberculous pleurisy, which results from an infection with Mycobacterium tuberculosis. This type remains prevalent in many parts of the world and often develops when latent TB becomes active and spreads to the pleura.
Another common infectious cause is bacterial pleurisy secondary to pneumonia. In these cases, a lung infection doesn't remain confined to the lung tissue but extends into the pleural cavity, leading to inflammation and fluid buildup. This progression underscores the importance of timely treatment for respiratory infections.
Viral and Autoimmune Contributors
Beyond bacterial agents, viral infections such as influenza, coxsackievirus, or even SARS-CoV-2 (the virus behind COVID-19) can lead to pleuritic pain and inflammation. Additionally, autoimmune disorders like lupus and rheumatoid arthritis are known to trigger pleurisy by causing the body's immune system to attack its own tissues, including the pleura.
Cancer-Related Pleural Inflammation
In more severe cases, pleurisy may be linked to malignancies. There are two primary ways cancer can affect the pleura: through primary tumors and metastatic spread.
A rare but aggressive example is pleural mesothelioma, a primary tumor originating in the pleural lining, often associated with long-term asbestos exposure. On the other hand, cancers from distant organs—such as the breast, lung, or lymphatic system—can metastasize to the pleura, causing reactive inflammation and significant discomfort.
Distinguishing Between Types of Pleurisy
Clinically, pleurisy presents in two main forms. The first is dry pleurisy, characterized by inflamed pleural surfaces rubbing against each other. This type commonly causes sharp, stabbing chest pain that worsens with breathing, coughing, or sneezing.
The second and more frequently observed form involves pleural effusion—a buildup of excess fluid in the pleural space. This fluid accumulation can compress the lungs, leading to shortness of breath, reduced oxygen intake, and increased risk of infection if left untreated. Diagnosing the nature of the fluid (transudative vs. exudative) helps determine the underlying cause and guides appropriate therapy.
Early diagnosis and targeted treatment are crucial in managing pleurisy effectively. Whether caused by infection, autoimmune disease, or cancer, understanding the root cause allows healthcare providers to tailor interventions that not only relieve symptoms but also address the condition at its source.