Autoimmune haemolytic anaemia complicating haematopoietic cell transplantation in paediatric patients: high incidence and significant mortality in unrelated donor transplants for non‐malignant diseases

Summary Haemolytic anaemia is a recognized complication of haematopoietic cell transplantation (HCT) and can result from alloimmune‐ or autoimmune‐derived antibodies. Unlike alloimmune haemolytic anaemia, autoimmune haemolytic anaemia (AIHA) is poorly understood, particularly in the paediatric population where only case reports have been published. Between January 1995 and July 2001, 439 consecutive allogeneic HCT were performed in paediatric patients at the University of Minnesota, 31% ( n = 136) from related donors (RD) and 69% ( n = 303) from unrelated donors (URD). Nineteen cases of AIHA were identified with documented significant haemolysis and a positive direct antiglobulin test. All cases of AIHA occurred in URD transplants, yielding a cumulative incidence of AIHA post‐transplant of 6% at 1 year. Patients transplanted for non‐malignant disease, particularly metabolic diseases, had a higher incidence of AIHA post‐HCT when compared with patients transplanted for malignancies (RR 4·2 95% CI 1·2–15·4, P = 0·01). Mortality was high in our series of 19 patients with 10 (53%) dying following the onset of AIHA, three as a direct consequence of haemolysis. Fifty per cent of deaths occurred from infection while on immunosuppressive therapy to treat haemolysis. Alternative treatment strategies were employed, with the majority of patients demonstrating disease refractory to traditional steroid therapy.