Why do acquired connective tissue diseases often affect the lungs?

Acquired connective tissue diseases often affect the lungs because these conditions frequently involve systemic inflammation or immunologic processes that target various organs and tissues throughout the body.12

In diseases such as systemic lupus erythematosus, organ damage occurs due to the deposition of immune complexes in specific areas, including the serous membranes surrounding the lungs. Similarly, rheumatoid arthritis can manifest as inflammation and nodule formation within the lung parenchyma or the pleura (the tissue covering the lungs).312

These inflammatory processes can lead to pulmonary fibrosis, a condition where dense fibrous connective tissue replaces healthy lung tissue. This scarring stiffens the lungs, reduces the space available for air, and impairs gas exchange, which can ultimately progress to respiratory failure. Additionally, because many of these diseases involve generalized inflammation of the blood vessels, the pulmonary vasculature is often susceptible to secondary damage.41