You have been treating a 33-year-old woman for asthma for the last three years. She began with mild symptoms, but has become progressively more short of breath over the last year. She reports weight loss and significant dyspnea on exertion. She has never smoked, but her husband smokes in the home. Her maternal aunt was a smoker, and died of emphysema in her early 50s. Her chest x-ray reveals flattened diaphragms, a long, narrow heart cardiac silhouette, and increased retrosternal airspace on the lateral projection. Given this clinical picture and x-ray, what is the most likely consideration?