Asthma: The FEV1/FVC ratio indicates a mild obstructive pattern, which is consistent with asthma, especially if symptoms such as wheezing, cough, and shortness of breath are present. The improvement after bronchodilator use further supports this diagnosis.

Chronic Obstructive Pulmonary Disease (COPD): Although less likely given the mild obstruction and significant response to bronchodilator, early or mild COPD could present similarly, especially in smokers or those with exposure to harmful substances.
Bronchiectasis: This condition can cause obstructive lung function tests due to chronic inflammation and damage to the bronchi, potentially presenting with a similar FEV1/FVC ratio.
Cystic Fibrosis: In its mild form, cystic fibrosis can present with obstructive lung disease, though other systemic symptoms and diagnostic tests would be necessary to confirm this diagnosis.

Pulmonary Embolism: Although pulmonary embolism typically presents with a normal or near-normal spirometry, in rare cases, it can cause obstructive patterns due to pulmonary infarction or other mechanisms. The clinical context (e.g., sudden onset of symptoms, risk factors for thromboembolism) is crucial.
Cardiac Disease: Conditions like heart failure can lead to pulmonary congestion and potentially mimic obstructive lung disease on spirometry, especially if there's associated wheezing ("cardiac asthma").

Alpha-1 Antitrypsin Deficiency: A genetic disorder that can lead to COPD-like symptoms and lung function abnormalities at a young age, even in non-smokers.
Eosinophilic Granulomatosis with Polyangiitis (Churg-Strauss Syndrome): A rare autoimmune condition that can cause asthma-like symptoms along with eosinophilia and vasculitis.
Lymphangioleiomyomatosis (LAM): A rare lung disease affecting mostly women, characterized by cystic lung lesions and can present with obstructive lung function.