Secondary autoimmune and inflammatory diseases after allogeneic hematopoietic stem cell transplantation: a retrospective study from the EBMT Complications Working Party (CWP).

Secondary autoimmune and inflammatory diseases (SAIDs) are underrecognized and poorly described after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The standardization of management is hindered by the scarcity of data on epidemiology, pathogenesis, and clinical outcomes. To improve the evidence base, we performed a retrospective multicenter EBMT database study of patients who underwent allo-HSCT between 2005 and 2019 for either hematological malignancy or severe aplastic anemia with available information on SAIDs. We included 129 cases of SAIDs and 14,617 controls. The 5-year incidence of SAIDs was 0.9% (95% confidence interval (CI): 0.7-1.1), and the 10-year incidence was 1.1% (95% CI: 0.9-1.3). The median time from allo-HSCT to the diagnosis of SAIDs was 442 days [interquartile range (IQR): 242-1082]. Overall survival after the onset of SAIDs was 83.4% (95% CI 74.6-89.3) at 2 years and 73.4% (95% CI: 62-82) at 5 years. In multivariate analysis, risk factors significantly associated with SAIDs were bone marrow failure (Hazard Ratio (HR): 3.41 [95% CI, 1.55-7.52], p = 0.002), female donor to male patient (HR 1.77 [95% CI, 1.15-2.73], p = 0.009), and the presence of chronic GvHD (HR 1.61 [95% CI, 1.04-2.51], p = 0.034). SAIDs after allo-HSCT are rare but clinically significant entities requiring further investigations, exploring treatment and prevention strategies, as well as improving diagnostic approaches.