Autoimmune hemolytic anemia (AIHA) after allogeneic hematopoietic stem cell transplantation (HSCT) is still not well characterized. The aim of this study was to analyze the incidence and risk factors for the development of AIHA, as well as its prognosis and response to treatment in a series of patients undergoing allogeneic HSCT at a single institution. Between 1996 and 2004, 272 adult patients with a variety of malignant hematopoietic disorders underwent allogeneic HSCT. Direct antiglobulin testing was performed in routine pretransfusion compatibility testing or after clinical suspicion of AIHA. Twelve patients developed AIHA after HSCT at a median time of 147 days (range, 41-170). The 3-year cumulative incidence of AIHA was 4.44%. Eight cold antibodies and four warm antibodies were detected. Multivariate analysis shows that HSCT from unrelated donors (P ¼ 0.02) and the development of chronic extensive graft-versus-host disease (GVHD) (P ¼ 0.0004) were the only independent factors associated with AIHA. Two patients are still alive. AIHA was never the primary cause of death but added morbidity in patients with other concomitant complications. Patients undergoing HSCT from unrelated donors and those who develop chronic extensive GVHD are especially predisposed for this complication.

This is the first reported case of severe immune hemolytic anemia due to multiple RBC alloantibodies after an allogeneic bone marrow transplant. The time of appearance and the specificity of the antibodies strongly suggest that they were produced by residual recipient lymphoid cells.

Summary. Twenty patients with thrombotic thrombocytopenic purpura (TTP) underwent plasma exchange using either standard fresh-frozen plasma (Group A, n 13) or methylene blue-treated plasma (Group B, n 7). Both groups presented similar characteristics except that bilirubin values were higher in Group A (P , 0´05). The complete remission rate was higher in Group A than B (69% versus 57%). The mean number of procedures was higher in Group B (21^7 versus 11^3, P , 0´01) and the mean duration of hospitalization was also longer (37^12 d versus 22^11 d; P , 0´01). Our study shows that the use of methylene blue-treated fresh-frozen plasma to treat TTP is associated with a higher number of plasma exchanges and greater transfusion requirements without improving clinical results.

These data show that the incidence of Wr(a) antigen and anti-Wr(a) among the population from Valencia is similar to that reported in other European areas and suggest that the development of anti-Wr(a) is facilitated by the presence of a hyperactive immune system. The clinical relevance of anti-Wr(a) is limited, however.

Patients undergoing allogeneic HPC transplantation are at risk of developing RBC-specific antibodies despite the immunosuppressive therapy administered. Antibody formation was more frequently observed in ABO-mismatched cases, which suggests a potential role of this incompatibility in facilitating antibody production.