The combination of sinus and lung disease is also seen in various types of pulmonary vasculitis. This could be suppressed by prednisone, even with the CT scan of the lungs returning to normal.
Your PFTs definitely show the findings of restrictive lung disease. A normal chest x-ray would not necessarily mean you do not have significant lung disease. You should have another CT scan. Talk about the findings with your pulmonary specialist before considering an open lung biopsy. To be sure of the diagnosis a biopsy will most likely be needed. However it may be possible to tell from a sinus mucosal biopsy. Hypersensitivity pneumonitis remains a possibility. A number of interstitial allergic and non-allergic lung diseases are also possibilities.
Good luck. Please give us a follow-up.
Sounds complicated. ABPM (allergic bronchopulmonary mycosis) is certainly a diagnostic possibility. What's odd about this is you don't have obstruction on your lung function test. (Obviously, you could expel the entire functional vital capacity within one second. (FVC = FEV1) People with significant airflow obstruction cannot do that.)
If all the test results are credible, we are discussing a restrictive pulmonary disorder that causes off-and-on inflammation of the lung tissue, a bit of bronchial inflammation and recurrent sinus infection. Pulmonary vasculitis syndromes, e.g. Wegener's granulomatosis and Churg-Strauss syndrome, would fit these description. You should at least have a blood test (ANCA) done, if not biopsy of the sinus +/- the lung for a definitive diagnosis.
A few other things also come to mind, i.e. primary ciliary dyskinesia and certain immunodeficiency states, in particular immunoglobulin deficiency. However, these disorders are usually associated with obstruction on the lung function test.
Severe gastroesophageal reflux disease can lead to recurrent aspiration pneumonia but I find it difficult to tie it to the sinus problems.
In summary, this is a complicated presentation and part of the picture has been modified by intermittent steroid treatments. I'd suggest that you work closely with your doctor and discuss with him/her about the possibility of pulmonary vasculitis and the role of sinus/lung biopsy to find out what you have for certain. Hope this helps.
Good luck,
HappyNeige...