Causes and Risk Factors of Pleurisy: A Comprehensive Overview
Understanding Pleurisy: What Triggers Inflammation of the Pleura?
Pleurisy, also known as pleuritis, occurs when the pleura—the thin layers of tissue lining the lungs and chest cavity—become inflamed. This condition can result from a wide range of underlying health issues, including infections, autoimmune disorders, malignancies, and exposure to environmental or chemical irritants. The inflammation leads to sharp chest pain, especially during breathing, and may be accompanied by other symptoms such as shortness of breath and persistent coughing.
Common Infectious Causes of Pleurisy
Infections are among the leading causes of pleural inflammation. Bacterial, viral, fungal, and parasitic agents can all invade the pleural space and trigger an immune response. Bacterial infections, particularly those caused by Mycobacterium tuberculosis, are responsible for a significant number of cases worldwide. Tuberculosis-related pleurisy remains one of the most prevalent forms of infectious pleuritis, especially in regions with high TB incidence.
Viral infections such as influenza, Epstein-Barr virus, and coxsackievirus are also frequent culprits, often following respiratory tract infections. Fungal pathogens like Aspergillus or Candida may affect immunocompromised individuals, while parasitic infections—including amoebiasis and lung fluke (Paragonimus westermani)—can spread to the pleura from other organs, causing localized inflammation.
Non-Infectious Conditions Linked to Pleural Inflammation
Beyond infections, several systemic and chronic diseases contribute to the development of pleurisy. Pneumonia and pulmonary embolism are two major non-infectious triggers, where lung tissue damage or reduced blood flow leads to secondary pleural irritation.
Autoimmune disorders play a critical role as well. Conditions like rheumatoid arthritis and systemic lupus erythematosus (SLE) can cause the body's immune system to attack the pleural membranes, resulting in recurrent episodes of inflammation. In lupus patients, this is often referred to as "lupus pleuritis" and may occur alongside other serositis manifestations.
Cancer, Pancreatitis, and Environmental Exposures
Malignant tumors, especially lung cancer and metastatic cancers that spread to the pleura, can induce pleurisy through direct invasion or fluid accumulation (malignant effusion). Similarly, acute pancreatitis may lead to pleural involvement due to the migration of inflammatory enzymes into the chest cavity via anatomical pathways.
Exposure to certain environmental toxins is another important factor. Long-term inhalation of substances like asbestos not only increases the risk of mesothelioma but can also cause chronic pleural thickening and inflammation. Occupational hazards in construction, shipbuilding, and manufacturing industries highlight the importance of protective measures.
Drug Reactions and Other Contributing Factors
Some medications can provoke hypersensitivity reactions that manifest as drug-induced pleurisy. Drugs such as hydralazine, procainamide, and certain chemotherapy agents have been associated with pleural inflammation, typically as part of a broader autoimmune-like response.
Additionally, chest trauma, post-surgical complications, and even radiation therapy to the chest area can irritate the pleura and initiate an inflammatory cascade. Recognizing these diverse etiologies is essential for accurate diagnosis and targeted treatment planning.
Conclusion: Identifying the Root Cause for Effective Management
Because pleurisy is a symptom rather than a standalone disease, identifying its underlying cause is crucial for effective intervention. A thorough medical evaluation—including imaging, laboratory tests, and sometimes pleural fluid analysis—is necessary to determine whether the origin is infectious, autoimmune, neoplastic, or environmental. Early detection and tailored therapy significantly improve patient outcomes and reduce the risk of complications such as pleural effusion or fibrosis.