question: Hello...My mom is suffering from Hypersensitivity pneumonitis, she was diagnosed with this disease 5 years back and got complete recovery however recently she started getting same symptoms and the CT is more severe than before...her pulmonologist has put her on prednisone and asked us to wait for 2-3 months to see how much she recovers. He hasn't asked for any other test except WBC count check.I am very much worried and wants to know the severity this time, Since her lower lungs show some honey combing (slight) + some amount of intralobular nodules and septal thickening, i am more worried. Though after studying many cases i have found that such CT images are present in HP patient. I just want to know what is the difference between Idiopathic pulmonary fibrosis and hypersensitivity pneumonitis. What kind of pathological tests determines the difference?