The prevalence of HPA-1a alloimmunization and the potential risk of FNAIT depend on both the DRB3*01:01 allele and associated DR-DQ haplotypes

Severe intracranial haemorrhage in neonatal alloimmune thrombocytopenia due to antibodies against human platelet antigen 1b: Case report and literature review

Fetal/neonatal alloimmune thrombocytopenia (FNAIT) is a rare life-threatening disorder, leading to severe thrombocytopenia and potentially bleeding, with intracranial haemorrhage (ICH) being the most serious complication. We report on a FNAIT case with fourth-degree ICH that arose due to antibodies against human platelet antigen (HPA)-1b. The male infant, born to an otherwise healthy mother, presented with severe signs of ICH soon after delivery. Since only moderate thrombocytopenia was noted and there were no active signs of bleeding, the infant did not receive intravenous immunoglobulins (IVIg) or platelet transfusion. Spontaneous recovery of platelets was noted on the eighth day of life, but permanent neurological impairment remained as a consequence of ICH. We report the results of HPA and human leukocyte antigen (HLA) antibodies in the mother's and the infant's sera, the family's HPA genotype and the mother's HLA genotype, and summarise previously described cases of FNAIT due to anti-HPA-1b antibodies in the literature. FNAIT with severe ICH due to anti-HPA-1b antibodies is rarely diagnosed. An association between HLA genes and sensitization to HPA-1b antibodies was not demonstrated. The severity of FNAIT and the occurrence of ICH is often difficult to predict. In this case, the infant presented with moderate thrombocytopenia and ICH, with subsequent permanent consequences.

Immunohematologic aspects of alloimmunization and alloantibody detection: A focus on pregnancy and hemolytic disease of the fetus and newborn

Alloimmunization to non-ABO, red blood cell (RBC) antigens remains one of the most clinically-relevant complexities faced by blood banking practitioners. In the setting of transfusion therapy, these antibodies raise risks for incompatibilities, while for pregnant patients they can mediate deadly forms of hemolytic disease of the fetus and newborn. As such, a thorough understanding of pathways that lead to alloimmunization, as well as the tools used by blood banks to detect alloantibodies, is critical to transfusion practice. In this review, in which alloimmunization in the setting of pregnancy will be emphasized, we will review: 1) the clinical impacts of RBC alloantibodies in the peri-partum period; 2) the current pathophysiologic mechanisms thought to influence non-ABO antigen alloimmunization; 3) the strengths and weaknesses of laboratory tools used in aiding alloimmunization detection; and 4) future directions of the transfusion community related to alloimmunization impacting pregnancy.