CASE PRESENTATION: A 65-year-old Caucasian male, retired school teacher with no significant past medical history presented with progressive dyspnea and dry cough over 2 weeks. He had a 20-pack-year history of smoking, but quit 20 years ago. Regular medications included fish oil and glucosamine for knee osteoarthritis. There is no family history of similar presentation or connective tissue disorders. He was born in Australia and currently lived in a regional area, but with no exposure to farm animals. He had 1 pet dog. Hobbies included woodwork and gardening with regular exposure to mulch hay and potting mix. There were no sick contacts otherwise. There was no sputum production, hemoptysis, fever, night sweats or flu-like illness. He did have intentional weight loss of 6 kilograms over the last 3 months. There were no myalgia, arthralgia, sicca symptoms, abdominal or urinary symptoms. The only pertinent clinical finding was bilateral inspiratory crepitations without accompanying signs of overt heart failure. Initial chest x-ray demonstrated widespread interstitial and alveolar opacities. There was mild leukocytosis with neutrophilia. Interestingly, there was also a transient mild borderline eosinophilia. Urinalysis, renal and liver functions were unremarkable. Antibiotics for community-acquired pneumonia and diuretic therapies resulted in no improvement. A computed tomography pulmonary angiogram (CTPA) showed no pulmonary embolus. However, significant homogeneous bilateral ground-glass opacities and non-specific sub-pleural nodular infiltrates were demonstrated. There were no consolidation or significant lymphadenopathies. Bronchoscopy with transbronchial biopsy revealed no endobronchial abnormalities. Biopsies showed alveolar space filling by fibrin and macrophages, hyperplastic pneumocytes and mildly expanded interstitium with mild chronic inflammatory infiltrates. There were no granuloma, hyaline membrane, oesinophils, inclusion bodies, fibrosis or malignancy. All bacterial, mycobacterial and fungal cultures were negative. Viral PCRs were also negative. Infectious, hypersensitivity and autoimmune serologies were insignificant. A diagnosis of AFOP was made and the patient was commenced on Methylprednisolone followed by long-term prednisolone and additional Mycophenolate mofetil therapy for 6 months. Follow-up for the last 10 months showed complete radiological resolution with normalization and stability of diffusing capacity for carbon monoxide and 6-minute walk test.