In patients with COP or BOOP, a solitary nodule or multiple nodules were detected radiologically. Akira reported that 53 of 60 nodular lesions detected in 12 BOOP patients had an irregular margin, and 27 had an air bronchogram. Therefore, he concluded that BOOP should be considered when imaging reveals nodular lesions with an air bronchogram and irregular margins [7]. Thus, the first type of AFOP was reported to have some clinical similarities with BOOP [8-10]. Corticosteroid therapy resulted in the improvement of nodular lesions and diffuse infiltrates. The disease in our patient may be classified as the subacute type of AFOP. The second type shows a more rapid progression and has clinical features similar to that of acute respiratory distress syndrome. Pulmonary complications account for significant morbidity and mortality in patients after HSCT, with an incidence rate of 70%, and are a contributing factor in more than 30% of transplant-related deaths [11]. With the advances in transplantation, the reports of noninfectious pulmonary complications have increased. However, there are a few reports on acute-onset noninfectious pulmonary complications following HSCT. Noninfectious pulmonary complications are the major causes of morbidity and mortality after allogeneic HSCT. Epidemiological data suggest that conditioning-related toxicity is the major contributing factor although GVHD may play a role. Among the noninfectious pulmonary complications, obli- terative bronchiolitis and BOOP are more closely associated with GVHD [12]. The other complications are pulmonary edema, engraftment syndrome, diffuse alveolar hemorrhage, and pulmonary veno-occlusive disease [1]. The uniqueness of this report is that it describes the first case of AFOP following allogeneic HSCT, and this condition may be a type of GVHD in the lung. Further information should be obtained about the clinical and radiological features of AFOP and the differences between AFOP and other acute interstitial lung disease. The present case report provides useful data about this new entity. Lee SM, et al. Acute fibrinous and organizing pneumonia 159 REFERENCES 1. Yen KT, Lee AS, Krowka MJ, Burger CD. Pulmonary complications in bone marrow transplantation: a practical approach to diagnosis and treatment. Clin Chest Med 2004;25:189-201. 2. Beasley MB, Franks TJ, Galvin JR, Gochuico B, Travis WD. Acute fibrinous and organizing pneumonia: a histological pattern of lung injury and possible variant of diffuse alveolar damage. Arch Pathol Lab Med 2002;126:1064-1070. 3. Prahalad S, Bohnsack JF, Maloney CG, Leslie KO. Fatal acute fibrinous and organizing pneumonia in a child with juvenile dermatomyositis. J Pediatr 2005;146:289-292. 4. Kobayashi H, Sugimoto C, Kanoh S, Motoyoshi K, Aida S. Acute fibrinous and organizing pneumonia: initial presentation as a solitary nodule. J Thorac Imaging 2005;20:291-293. 5. Bleyl U, Sander E, Schindler T. The pathology and biology of uremic pneumonitis. Intensive Care Med 1981;7:193-202. 6. American Thoracic Society, European Respiratory Society. American Thoracic Society/European Respiratory Society International Multidisciplinary Consensus Classification of the Idiopathic Interstitial Pneumonias. Am J Respir Crit Care Med 2002;165:277-304. 7. Akira M, Yamamoto S, Sakatani M. Bronchiolitis obliterans organizing pneumonia manifesting as multiple large nodules or masses. AJR Am J Roentgenol 1998;170:291-295. 8. Chee CB, Da Costa JL, Sim CS. A female with dry cough, progressive dyspnea and weight loss. Eur Respir J 2005;25: 206-209. 9. Poletti V, Casoni GL. Cryptogenic organising pneumonia or acute fibrinous and organising pneumonia? Eur Respir J 2005;25:1128. 10. Cordeiro CR. Airway involvement in interstitial lung disease. Curr Opin Pulm Med 2006;12:337-341. 11. Wah TM, Moss HA, Robertson RJ, Barnard DL. Pulmonary complications following bone marrow transplantation. Br J Radiol 2003;76:373-379. 12. Watkins TR, Chien JW, Crawford SW. Graft versus host- associated pulmonary diasesa and other idiopathic pulmonary complications after hematopoietc stem cell transplant. Semin Respir Crit Care Med 2005; 26:482-489.