A 19-year-old man is referred to a pulmonology clinic after two emergency department visits in the past year for episodic wheezing and shortness of breath with exercise. He does not smoke. Between episodes, he has no symptoms at rest. On examination today, his lungs are clear to auscultation bilaterally without wheezes. Spirometry is performed: FEV₁ 1.8 L (62% of predicted), FVC 3.2 L (88% of predicted), FEV₁/FVC ratio 0.56.
Which of the following best characterizes this patient's spirometric pattern and severity?