Red blood cell alloimmunization in sickle cell anemia: more questions than answers?

Improvement of maternal and fetal outcomes in women with sickle cell disease treated with early prophylactic erythrocytapheresis

BACKGROUND

The desire for pregnancy in sickle cell disease (SCD) women has become a true challenge for hematologists, requiring a multidisciplinary approach. Erythrocytapheresis (ECP) is an important therapeutic tool in SCD, but only limited data on starting time and the effects of ECP during pregnancy are available.

STUDY DESIGN AND METHODS

This is a double-center retrospective cross-sectional study on a total of 46 single pregnancies in SCD women from January 2008 to June 2017. ECP was started at 10.7 ± 5.2 weeks of gestation, and prophylactic enoxaparin (4,000 U daily) was introduced due to the reported high prevalence of thromboembolic events in pregnant SCD women.

RESULTS

The alloimmunization ratio was 2.1 per 1,000 and the alloimmunization rate was 5.6%. In early ECP-treated SCD women, no severe vaso-occlusive crisis, sepsis or severe infection, or preeclampsia or eclampsia were observed. We found normal umbilical arterial impedance during pregnancy, suggesting an optimal uteroplacental function in early ECP-treated SCD women. This was also supported by the improvement in newborn birthweights compared to previous studies. In our cohort, three SCD women were started later on ECP (20-25 weeks), and gestation ended with late fetal loss. Placenta pathology documented SCD-related damage and erythroblasts in placental vessels, indicating fetal hypoxia.

CONCLUSIONS

Collectively, our data generate a rationale to support a larger clinical trial of early ECP program in SCD pregnancy.

Red blood cell alloimmunization in 184 patients with myeloid neoplasms treated with azacitidine - A retrospective single center experience

Alloimmunization to Red Blood Cell (RBC) antigens frequently occurs in patients with myeloid neoplasms (AML, MDS and CMML) and potentially poses the patient at risk for delayed hemolytic transfusion reactions and limited supply of compatible RBC-units. However, there is comparatively little data on transfusion associated characteristics in this patient cohort. We therefore retrospectively analyzed transfusion requirements and clinical outcomes of 184 patients with myloid neoplasms treated with azacitidine at the Paracelsus Medical University Salzburg, which were included in the Austrian Registry of Hypomethylating Agents. The mean blood component requirements for AML, MDS and CMML were 39.8, 67.4 and 31.4 RBC units and 31.7, 27.6 and 19.1 platelet (PLT) units respectively. In spite of an extended and stringent RBC unit matching policy (ABO, RhD, RhCcEe and K antigens), 20 (11%) patients formed at least one alloantibody ("allo-group"), whereas 164 patients (89%) did not ("non-allo-group"). The most frequent antibody specificity was anti-E, followed by anti-Wra -Lua, -D, -C and -Jka. Alloimmunization was associated with higher numbers of transfused RBC units (68 vs. 38; p=0.001), as well as with longer time under transfusion (16.7 vs. 9.4 months; p=0.014). Median overall survival (OS) did not differ significantly between the "allo"- and "non-allo-group".

Red blood cell alloimmunization in sickle cell disease and in thalassaemia: current status, future perspectives and potential role of molecular typing

Red blood cell (RBC) transfusions are a milestone in the treatment for sickle cell anaemia (SSA) and for thalassaemia. RBC alloimmunization remains a major challenge of chronic transfusion therapy, and it can lead to adverse life-threatening events. The alloimmunization risk could depend on multiple factors such as the number of transfusions and, most of all, the genetic background. Different ethnic groups are predisposed to immunization because of a significant degree of RBC antigenic mismatch between donor and recipient. There is no universal agreement and standards for the most appropriate selection of RBC units in chronically transfused subjects. Current practice only deals with compatibility of ABO, Rh and K antigens. Molecular RBC antigenic matching extended to other blood group systems is an innovative strategy to ensure a better quality and effectiveness of transfusion therapy.