A 30 year old woman has episodic shortness of breath with chest tightness. Symptoms have been on and off for two years and have worsened for the last two to three months. No exercise induced or nocturnal symptoms. Family history of asthma. Roommate has dog and cat. Patient now has mild expiratory wheezing. What is the diagnosis and the tests to confirm the diagnosis? What are 3 differential diagnosis and the pathogenic mechanisms responsible for wheezing, chest tightness and SOB?