What causes restrictive lung diseases such as fibrosis?

Restrictive lung diseases, such as pulmonary fibrosis, are characterized by a decrease in the total lung capacity and hindered expansion of the lungs due to structural changes in the lung tissue. The correct choice highlights tissue damage and irritation as the primary causes of these diseases. In conditions like pulmonary fibrosis, the lung tissue undergoes scarring (fibrosis) from inflammation or injury, leading to stiffening of the lung parenchyma. This stiffening reduces the lungs' ability to expand fully during inhalation, resulting in decreased oxygenation and restricted airflow.

The other options primarily focus on mechanisms that are more characteristic of obstructive lung diseases, where airflow is impeded due to blockages in the airways rather than damage to the lung tissue itself. For example, bronchoconstriction and mucus production contribute to obstructive conditions like asthma. Infection and airway inflammation may also lead to temporary conditions or exacerbate obstructive diseases but are not the main drivers of restrictive lung pathologies. Hence, while these factors are critical in respiratory health, they do not accurately describe the underlying mechanisms of restrictive lung diseases. The focus on tissue damage and irritation correctly aligns with the pathological processes involved in conditions like pulmonary fibrosis.