INTRODUCTION: Acute fibrinous and organizing pneumonia (AFOP) is a rare form of idiopathic interstitial pneumonia (IIP), which is now increasingly more recognized and has recently been added to the American Thoracic Society/European Respiratory Society international multidisciplinary classification of IIP. It is still regarded as a rare histologic pattern and is not yet classified as a new separate IIP entity.  Questions remain whether it is merely a histologic variant of existing IIPs or occurs in relation to other diseases such as hypersensitivity pneumonia or connective tissue disorder. It may also represent a histologic pattern that occurs in the clinical spectrum of diffuse alveolar damage and organizing pneumonia, and may reflect a tissue sampling issue. We report our experience with a case of AFOP treated successfully with corticosteroid and mycophenolate mofetil. 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 inAustralia 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 with out accompanying signs of overt heart failure. Initial chest x-ray demonstratedwidespread interstitial and alveolar opacities. There was mild leukocytosis with neutrophilia. Interestingly, there was also a transientmild 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 andmacrophages, hyperplastic pneumocytes andmildly expanded interstitium withmild 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 longterm 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. DISCUSSION: The classification of AFOP as a separate disease entity is still unclear, as it may belong to a spectrum of other interstitial pneumonias. Our experience posed a similar diagnostic challenge. There were risk factors and radiological evidence for hypersensitivity pneumonia, but histological and serological evidence were lacking. There has been a similar case report in which combined corticosteroid and mycophenolate therapy proved successful.  Our patient also received a similar therapy with success. CONCLUSION(S): AFOP is a rare form of idiopathic interstitial pneumonia. Combined corticosteroid and mycophenolate therapy may be effective in its treatment.
Kruavit, A., Pearson, R., & Heraganahally, S. (2016). A Rare Case of Idiopathic Interstitial Pneumonia With Good Outcome: Acute Fibrinous and Organizing Pneumonia. Chest, 150(4), 280A. https://doi.org/10.1016/j.chest.2016.08.293