Delayed severe HPA-5b neonatal alloimmune thrombocytopenia: A case report

In 1988, a new platelet-specific alloantigen, HPA5b (Br) was first described in four cases of neonatal alloimmune thrombocytopenia (NAIT) [1], and a new platelet system, HPA-5a/b (Br/ Br) characterized [2]. In NAIT, anti-HPA-1a antibody was more frequently observed and more severe for the fetus and the newborn than antiHPA-5b [3–5]. Nevertheless, in 39 cases of antiHPA-5b NAIT, Kaplan et al. found three newborns who developed intracranial hemorrhage (ICH) and one died, probably due to the ICH (intracranial hemorrhage) [6]. Recently, among 31 cases in Quebec, no ICH was observed, but two newborns needed treatment, one with intravenous human immunoglobulin (IVIG) only and, the other with IVIG and platelet transfusion [7]. Campbell-Lee et al. reported a case of anti-HPA-5b maternal alloimmunization treated with IVIG therapy and intrauterine treatment of the fetus by platelet transfusion at 28 weeks of gestation [8]. Further, Herrero et al. [9] have reported the efficiency of IVIG treatment in an HPA-5b alloimmunized mother with an HPA-5b thrombocytopenic fetus and without a previously affected baby. This report considers a case of delayed anti-HPA-5b thrombocytopenia with ICH requiring platelet transfusion, manifested five days after birth. A 34-year-old mother, gravida 2/para 2, gave birth to a male neonate by cesarean section at 34 weeks of gestation because of intrauterine growth retardation (IUGR) and anamniotic fetus. Five years before, she had had a first pregnancy with IUGR of the fetus but without NAIT. The second neonate weighed 1350 g, was 41.0 cm long, and had a head circumference of 27.5 cm. The Apgar scores were 9, 10, 10, and 10 at 1, 3, 5, and 10 minutes after birth, respectively. No bleeding, hepatomegaly, splenomegaly or infectious signs were noted. Five hours after birth, a respiratory distress syndrome developed and oxygen therapy was administered for 44 hours. The platelet count, which was 82, 79, and 73610/L on days 0, 1, and 2, respectively, dropped dramatically on day 5 to 9610/L. Simultaneously, an ICH grade II was diagnosed on ultrasound scan. Platelets were transfused to the baby and the platelet count rose to 80, 115, and 315610/L on days 6, 10, and 18 respectively. No further transfusion was needed and the development of the baby was satisfactory with a normal electroencephalogram. A solid phase red blood cell (RBC) adherence assay (Modified Capture P, Immucor, Norcross, GA, USA) was used to screen for platelet antibodies. Pooled platelets collected from ten selected blood donors phenotyped for the main platelet antigen systems (HPA-1, -3, and -5) were used for plateletspecific allo-antibody testing and patient platelets for platelet-specific auto-antibodies. The platelet-specific antibodies were characterized by the monoclonal antibody specific immobilization of platelet antigen (MAIPA) assay [10] on microplates. Three main platelet antigen systems (HPA-1, -3, and -5) were investigated. Donor platelets were used for the allo-antibody identification and the patient’s platelets for the auto-antibody characterization. Three platelet glycoproteins (GP) were evaluated with three murine monoclonal antibodies: GP Ia IIa, GP IIb IIIa, and GP Ib IX. When a positive reaction was obtained with one or more GPs, a second step using a panel of ten platelet donors tested in the HPA-1, -3, and -5 systems was initiated in order to characterize the specificity of the plateletspecific antibodies. The Journal of Maternal-Fetal and Neonatal Medicine, January 2007; 20(1): 75–76