1064 Arch Pathol Lab Med—Vol 126, September 2002 Acute Fibrinous and Organizing Pneumonia—Beasley et al Acute Fibrinous and Organizing Pneumonia A Histologic Pattern of Lung Injury and Possible Variant of Diffuse Alveolar Damage Mary Beth Beasley, MD; Teri J. Franks, MD; Jeffrey R. Galvin, MD; Bernadette Gochuico, MD; William D. Travis, MD ● Context.—The histologic patterns of diffuse alveolar damage (DAD), bronchiolitis obliterans with organizing pneumonia (BOOP), and eosinophilic pneumonia (EP) are well-recognized histologic patterns of lung injury associ- ated with an acute or subacute clinical presentation. We have recognized acute fibrinous and organizing pneumo- nia (AFOP) as a histologic pattern, which also occurs in this clinical setting but does not meet the classic histologic criteria for DAD, BOOP, or EP and may represent an un- derreported variant. Objectives.—To investigate the clinical significance of the AFOP histologic pattern and to explore its possible re- lationship to other disorders, including DAD and BOOP. Design.—Open lung biopsy specimens and autopsy specimens were selected from the consultation files of the Armed Forces Institute of Pathology, which showed a dom- inant histologic pattern of intra-alveolar fibrin and orga- nizing pneumonia. Varying amounts of organizing pneu- monia, type 2 pneumocyte hyperplasia, edema, acute and chronic inflammation, and interstitial widening were seen. Cases with histologic patterns of classic DAD, BOOP, ab- scess formation, or eosinophilic pneumonia were excluded. To determine the clinical behavior of patients with this his- tologic finding, clinical and radiographic information and follow-up information were obtained. Statistical analysis was performed using Kaplan-Meier and x 2 analysis. Results.—Seventeen patients (10 men, 7 women) with a mean age of 62 years (range, 33–78 years) had acute-onset symptoms of dyspnea (11), fever (6), cough (3), and he- moptysis (2). Associations believed to be clinically related to the lung disease included definitive or probable collagen vascular disease (3), amiodarone (1), sputum culture pos- itive for Haemophilus influenza (1), lung culture positive for Acinetobacter sp. (1), lymphoma (1), hairspray (1), con- struction work (1), coal mining (1), and zoological work (1). Six patients had no identifiable origin or association. Follow-up revealed 2 clinical patterns of disease progres- sion: a fulminate illness with rapid progression to death (n 5 9; mean survival, 0.1 year) and a more subacute illness, with recovery (n 5 8). Histologic analysis and initial symp- toms did not correlate with eventual outcome, but 5 of the 5 patients who required mechanical ventilation died (P 5 .007). Conclusions.—Acute fibrinous and organizing pneumo- nia is a histologic pattern associated with a clinical picture of acute lung injury that differs from the classic histologic patterns of DAD, BOOP, or EP. Similar to these patternsof acute lung injury, the AFOP pattern can occur in an idio- pathic setting or with a spectrum of clinical associations. The overall mortality rate is similar to DAD and therefore may represent a histologic variant; however,AFOP appears to have 2 distinct patterns of disease progression and out- come. The need for mechanical ventilation was the only parameter that correlated with prognosis. None of the pa- tients with a subacute clinical course required mechanical ventilation. (Arch Pathol Lab Med. 2002;126:1064–1070) C lassification of biopsy specimens from patients with a clinical picture of acute lung injury often presents a difficult diagnostic challenge. Diffuse alveolar damage (DAD) and bronchiolitis obliterans with organizing pneu- monia (BOOP) are well-recognized histologic patterns as- sociated with an acute or subacute clinical presentation, respectively. Both the DAD and BOOP patterns may be Accepted for publication April 24, 2002. From the Departments of Pulmonary and Mediastinal Pathology (Drs Beasley, Franks, and Travis) and Radiologic Pathology (Dr Galvin), Armed Forces Institute of Pathology, and Pulmonary-Critical Care Med- icine Branch of the National Heart, Lung, and Blood Institute (Dr Go- chuico), Washington, DC. Reprints: William D. Travis, MD, Department of Pulmonary and Me- diastinal Pathology, Armed Forces Institute of Pathology, 6825 NW 16th St, Washington, DC 20306-6000 (e-mail: Travis@afip.osd.mil). associated with known causes, such as collagen vascular diseases, or they may be idiopathic. 1 In a recently pro- posed multidisciplinary consensus classification spon- sored jointly by the American Thoracic Society (ATS) and the European Respiratory Society (ERS), idiopathic DAD may be referred to as acute interstitial pneumonia and idiopathic BOOP may be referred to as cryptogenic orga- nizing pneumonia (COP). 2 This ATS/ERS statement also recommended using the term organizing pneumonia (OP) for the histologic pattern, rather than BOOP. 2 Eosinophilic pneumonia (EP) may also present clinically as an acute or subacute illness in the form of acute EP and chronic EP, respectively. 1,3 We have encountered a histologic pattern associated with an acute or subacute clinical presentation, which does not meet the criteria for the patterns of DAD, OP, or EP, but instead is composed of predominantly intra-alve-