Which of the following conditions is characterized by reduced lung expansion?

The condition characterized by reduced lung expansion is interstitial lung disease. This group of disorders affects the tissue and space around the air sacs of the lungs (the interstitium), leading to stiffness and scarring of lung tissue. As a result, the lungs lose their ability to expand fully when inhaling, leading to a decrease in lung volumes and impaired gas exchange. The reduced lung expansion can cause symptoms such as shortness of breath and a persistent dry cough.

In contrast, other conditions like bronchitis and asthma primarily involve obstruction of the airways rather than the lung tissue itself. Emphysema, while also a lung disease, is more associated with the destruction of the air sacs (alveoli) and primarily leads to airflow limitation rather than reduced lung volume due to structural lung changes. Thus, interstitial lung disease is the key condition linked to the hallmark of reduced lung expansion.