Low alpha-1 antitrypsin leads to unchecked elastase activity in emphysema

Steps:

• Low alpha-1 protein allows elastase to degrade elastic fibers in alveoli and bronchioles.
• Degraded fibers cause alveolar wall destruction, reducing surface area for gas exchange.
• Loss of elasticity impairs lung recoil, leading to bronchiolar collapse on exhalation and air trapping.
• Trapped air and poor ventilation result in hypoxemia, stimulating rapid breathing.

Why A is correct:

• Emphysema definition includes all three: alveolar destruction (2), air trapping from collapse (3), and hypoxemia-driven tachypnea (1) due to elastase-mediated damage.

Why the others are wrong:

• B omits 2, but elastic fiber breakdown directly destroys alveolar structure.
• C omits 2 and 3, ignoring core pathology of tissue loss and air trapping.
• D omits 1, but hypoxemia from reduced gas exchange causes compensatory rapid breathing.

Final answer: A