Risk factors and outcomes of definite or clinical idiopathic pneumonia syndrome after allogeneic hematopoietic stem cell transplantation.

Idiopathic pneumonia syndrome (IPS) is a fatal pulmonary complication after allogeneic hematopoietic stem cell transplantation (allo-HCT). However, it is often difficult to diagnose IPS, since a considerable number of IPS patients are critically ill, which makes it difficult for them to undergo bronchoscopy. In this study, we explored the risk factors of IPS based on two definitions. Definite IPS was diagnosed based on the results of bronchoscopy, whereas clinical IPS was diagnosed based on the clinical condition and bronchoscopy was not mandatory. Among 444 allo-HCT recipients at our center, 30 definite IPS and 54 clinical IPS were identified. In a multivariable analysis, a high ferritin level was associated with a higher incidence of definite IPS, whereas clinical IPS was frequently associated with older age, MAC, high ferritin level, low %DLCO and second allo-HCT due to graft failure. These risk factors may contribute to the accurate and early diagnosis of IPS.