Characteristics and outcomes of autoimmune hemolytic anemia after pediatric allogeneic stem cell transplant

Background: Autoimmune hemolytic anemia (AIHA) after allogeneic hematopoietic stem cell transplant (HSCT) is a rare but complex and serious complication. Detailed descriptions of cases and management strategies are needed due to lack of prospective trials. Objectives: Describe the incidence, clinical characteristics, and management of AIHA after HSCT in a pediatric cohort. Methods: This is a retrospective cohort study of 33 pediatric patients with AIHA after HSCT at an academic tertiary care center from 2003 to 2019. A case-control analysis was performed to compare outcomes. Results: The overall incidence of AIHA after allogeneic HSCT was 3.8% (33/868). AIHA was significantly more common after transplant for non-malignant versus malignant diagnoses (7.0% (26/370) vs. 1.4% (7/498), p<0.0001). AIHA developed at a median of 4.7 months (range: 1.0-29.7) after transplant. Sixteen of 33 patients (48.5%) required new AIHA-directed pharmacologic therapy; 17 (51.5%) were managed on their current immunosuppression and supportive care. Patients managed without additional therapy were significantly older, more likely to have a malignant diagnosis, and tended to develop AIHA at an earlier timepoint after transplant. Patients received a median of 2 red blood cell transfusions within the first two weeks of diagnosis and a median of one AIHA-directed medication (range: 1-4), most commonly corticosteroids and rituximab. Conclusions: AIHA after HSCT is rare but occurs more commonly in patients transplanted for non-malignant diagnoses. While some patients can be managed on current immunosuppression and supportive care, many require AIHA-directed therapy including second-line medications.