RESUMEN
Cryptogenic organic pneumonia (COP) refers to organic pneumonia that has not been identified a clear cause by current medical methods. A small proportion of COP can exhibit severe and progressive characteristics, while severe COP can cause systemic inflammatory storms and can be secondary to hemophilia. This article reported a case of acute severe COP secondary to hemophilia. A 67-year-old male patient was admitted to the hospital due to cough, shortness of breath, and fever. At first, he was misdiagnosed as severe pneumonia, but failed to receive anti infection treatments. Sputum pathogenetic examination and Macrogene testing of alveolar lavage fluid were performed, and no etiology was found to explain the patient's condition. The condition was gradually worsened and hemophilia occurred to explain, suggesting that acute severe COP was relevant. After receiving hormone treatment, the condition gradually relieved and the absorption of lung lesions improved. Hemophilia secondary to COP is rare, and the specific mechanism needs further study.