An unusual case of severe neonatal thrombocytopenia.

Neonatal alloimmune thrombocytopenia (NAIT) occurs when maternal antibodies are directed against antigens on fetal and paternal but not maternal platelets. Most cases of NAIT arise when platelets of the father (and the fetus) express the human platelet antigen (HPA)1a and the mother's platelets expresses HPA-1b. A female patient presented with congenital severe thrombocytopenia and received 4 platelet transfusions, on days 2, 7, 16, and 28. This appeared to be a case of NAIT; however, extensive serologic evaluation by 2 reference laboratories failed to reveal the offending platelet antigen. Consistent with NAIT, the condition resolved by 6 weeks of age. By patient day of life 42, the platelet count had increased without additional need for transfusions, and by 16 weeks, the patient had a completely normal platelet count of 437,000/microL. The patient's platelet count remains normal at a 2-year follow-up. This case is reported as an instructive atypical case of NAIT, in which the relevant platelet antigen could not be identified.

A case report of neonatal alloimmune thrombocytopenic purpura: the importance of correct diagnosis for future pregnancies

CONTEXTO: Púrpura trombocitopênica neonatal aloimune (PTNA) é uma doença neonatal caracterizada por aloimunização materna contra as plaquetas fetais, que apresentam antígenos herdados do pai. Podem ocorrer hemorragias cerebrais, levando à morte ou a anomalias neurológicas permanentes. RELATO DE CASO: Mulher saudável, de 30 anos, deu à luz, por parto cesariano na 36ª semana de gestação, seu primeiro filho. Com 10 horas de vida, o recém-nascido apresentou petéquias e contagem de 8 x 103 plaquetas/µl no sangue periférico; foi medicado com imunoglobulina e recebeu alta após 18 dias de internação, com 100 x 103 plaquetas/µl. A causa da trombocitopenia não foi elucidada na época. Um ano depois, a criança morreu de neuroblastoma. Como os pais desejavam outro filho, foram encaminhados para investigação da trombocitopenia. Genotipagem plaquetária e pesquisa de anticorpos antiplaquetários foram realizadas, mostrando total falta de concordância entre os sistemas HPA-1 do pai (HPA-1a1a) e da mãe (HPA-1b1b) e anticorpos anti-HPA-1a no soro da mãe. Concluímos que o primeiro bebê nasceu com PTNA. Por isso, na segunda gravidez, a mãe foi tratada com diversas infusões de imunoglobulina intravenosa. Foi realizado cuidadoso monitoramento por ultra-som, com resultados normais para mãe e feto durante a gravidez. O segundo bebê nasceu por cesárea às 39 semanas, apresentando 92 x 103 plaquetas/µl seis horas após o nascimento. As plaquetas do recém-nascido foram genotipadas como HPA-1a1b e o soro da mãe novamente mostrou anticorpos anti-HPA-1a. Não houve hemorragia. A terapia de infusão de imunoglobulina foi efetiva na prevenção da PTNA no segundo filho.

A case report of neonatal alloimmune thrombocytopenic purpura: the importance of correct diagnosis for future pregnancies.

CONTEXT: Neonatal alloimmune thrombocytopenic purpura (NAITP) is a neonatal disorder characterized by maternal alloimmunization against fetal platelet antigens inherited from the father. Intracranial hemorrhage leading to death or permanent neurological disability may occur in the fetus. CASE REPORT: A healthy 30-year-old woman gave birth to her first baby by cesarean after an uneventful 36-week pregnancy. Ten hours after birth, the infant presented severe petechiae, with platelet count of 8 x 10(3)/microl. The mother's platelet count was normal (180 x 10(3)/microl). The infant re ceived intravenous immunoglobulin and was discharged 18 days later, with platelet count of 100 x 10(3)/microl. The cause of thrombocytopenia was not elucidated at that time. One year later, the infant died of neuroblastoma. Since the parents wanted another child, they were referred for investigation of this thrombocytopenia. Platelet genotyping and platelet antibody screening were performed, showing total HPA-1 system mismatch between mother (HPA-1b1b) and father (HPA-1a1a), with anti-HPA-1a antibodies in the mother's serum. We concluded that the first baby was born with NAITP. Thus, in the second pregnancy, the mother was treated with several infusions of intravenous immunoglobulin. Careful ultrasound monitoring was performed, with normal results for mother and fetus throughout the pregnancy. The second baby was born by cesarean at 39 weeks, presenting 92 x 10(3) platelets/microl six hours after birth. The baby's platelets were genotyped as HPA-1a1b and the mother's serum again showed anti-HPA-1a antibodies. No clinical bleeding was observed. Intravenous immunoglobulin therapy was an effective treatment for preventing NAITP in the second baby.

Low prevalence of a polymorphism of platelet membrane glycoprotein Ib beta associated with neonatal alloimmune thrombocytopenic purpura in Asian populations.

Iy alloantigen system is the first polymorphism of platelet glycoprotein Ib beta reported to cause neonatal alloimmune thrombocytopenic purpura. We investigated the allelic frequency of Iy alloantigen among Japanese and Korean populations by polymerase chain reaction-restriction fragment length method to determine the possibility of alloimmunization against Iy. Two hundred and nine Japanese and 97 Korean subjects were examined. All 306 individuals were homozygous for glycine at amino acid position 15 and negative for Iy. The allelic frequency of Iy in these populations was calculated to be less than 0.0016. Alloimmunization associated with Iy antigen in Asian populations seems unlikely from these results.

The fetal and neonatal consequences of maternal alloimmune thrombocytopenia.

Alloimmune thrombocytopenia is a relatively common and under-recognized entity. Prospective screening studies have suggested that at least 1 in every 1000 babies will be affected. While the severity of prospectively identified neonates is not as great as those 'routinely' identified as newborns, the incidence of intracranial haemorrhage in the fetus and neonate is the highest for any immune thrombocytopenia. Diagnosis is complex for the laboratory in view of the large number of platelet antigens and the importance of having sufficient numbers of typed controls. The importance of identifying the affected newborn extends to the likely need for antenatal management of the subsequent affected fetus. Studies to determine the optimal approach to this problem are ongoing. Ideally, prenatal screening of all pregnant women could be performed but this is not currently in practice.

Micromegakaryocytes in a patient with partial deletion of the long arm of chromosome 11 [del(11)(q24.2qter)] and chronic thrombocytopenic purpura.

Thrombocytopenia or pancytopenia is frequently reported in patients with partial 11q deletion but there are no reports on bone marrow morphology of these patients. We report on a patient with partial deletion of the long arm of chromosome 11 [del(11)(q24.2qter)] and its classical clinical manifestations including chronic thrombocytopenic purpura in whom micromegakaryocytes were found in the bone marrow aspirate. This is the first report of the presence of micromegakaryocytes in the bone marrow of a patient with 11q deletion. Accurate examination of the bone marrow of other patients with the 11q deletion may clarify whether the observation of micromegakaryocytes is common in these patients. Micromegakaryocytes may indicate a defect of development. Two genes for two DNA binding proteins that are likely to be involved in hematopoiesis map in the 11q region: Ets-1, that maps to 11q24, close to D11S912, and the nuclear-factor-related-kB gene that maps to 11q24-q25. It is possible that these genes, when present in only one copy, result in thrombocytopenia or pancytopenia as observed in this patient.

A new private platelet antigen, Groa, localized on glycoprotein IIIa, involved in neonatal alloimmune thrombocytopenia.

The serum of a Caucasian woman who gave birth to a child with neonatal alloimmune thrombocytopenia contained antibodies directed against a platelet antigen of the newborn. There was no incompatibility for the known platelet alloantigens HPA-1 to HPA-7 or for the private or low-frequency antigens Sra and Vaa, between the platelets of the parents. However, crossmatching with the serum of the mother and the platelets of the child and the father was strongly positive, suggesting a new platelet antibody specificity. To investigate the inheritance of the 'Groa' antigen involved, the available family members were tested in the platelet immunofluorescence test (PIFT) and the monoclonal antibody-specific immobilization of platelet antigens (MAIPA) assay. The Groa antigen was found to be inherited in an autosomal-codominant fashion. In the MAIPA, we localized the Groa antigen on the glycoprotein IIb/IIIa complex (alpha IIb beta 3). The GP IIb/IIIa localization was confirmed in immunoprecipitation studies. In Western blotting experiments, we further localized the Groa antigen on the GP IIIa (beta 3) subunit of the GP IIb/IIIa complex. Until now we have tested approximately 400 unrelated donors. None of these appeared to be positive for the Groa antigen, suggesting a phenotype frequency in the Dutch population of less than 0.01.

Alloimmunization to platelet antigen HPA-1a (PIA1) is strongly associated with both HLA-DRB3*0101 and HLA-DQB1*0201.

Antibodies to the platelet HPA-1a antigen can elicit in the newborn a condition known as neonatal alloimmune thrombocytopenic purpura (NAITP). Previous studies based on RFLP analysis showed that 100% of HPA-1a-negative women who produced anti-HPA-1a antibodies (responders) were HLA-DRw52a (DRB3*0101). However, this specificity could also be found in some HPA-1a-negative women not producing anti-HPA-1a antibodies (nonresponders). We have analyzed in detail by PCR-SSOP the HLA-DR, -DQ, and -DP loci of 36 responders and 10 nonresponders. We found that while the allele DRB3*0101 was present in the vast majority of responders (91%), there were exceptions. Furthermore, the DQB1*0201 allele was found to be present in almost all responders (94%), but again was also found in nonresponders. The risk of alloimmunization to HPA-1a in an HPA-1b homozygous mother significantly increases with the presence of either allele, the odds ratio being 39.7 for DQB1*0201 and 24.9 for DRB3*0101. Sequencing of exon 2 of these two alleles from responders indicated no sequence difference when compared with the consensus sequences. This indicates that they do not represent variants when compared with the same alleles found in some nonresponders.

A monoclonal antibody (LK-4) which differentiates PLA1 from PLA2 platelet extracts but not intact platelets.

A unique murine monoclonal antibody (LK-4) is described which differentiates PLA1/PLA1 platelet extracts from PLA2/PLA2 and PLA1/PLA2 platelet extracts on solid phase ELISA and immunoblot at the 100kD GPIIIa location, but not on intact platelets. LK-4 reacts equally with intact PLA1/PLA2 and PLA2/PLA2 platelets. Adsorbtion of LK-4 with PLA1/PLA1 platelets results in loss of reactivity for intact platelets as well as platelet extracts on ELISA or immunoblot. LK-4 inhibits platelet aggregation induced by ADP, epinephrine, collagen and thrombin, suggesting reactivity at or near the fibrinogen binding site on GPIIIa. It is suggested the LK-4 reacts with a conformation-induced common epitope for PLA1 and PLA2 on GPIIIa, with loss of this conformation for PLA2 GPIIIa following solubilization with Triton X-100.

Pregnancy in women with immune thrombocytopenic purpura.

Thirty-six women with immune thrombocytopenic purpura were studied during 37 pregnancies, and maternal characteristics with predictive value for the fetal platelet count were determined. Nine neonates were thrombocytopenic, with a platelet count of less than 50 x 10(9)/L in eight. Four of these nine neonates delivered to a subgroup of 31 mothers were studied prospectively; the frequency of thrombocytopenia in neonates of women with immune thrombocytopenic purpura was thus 13%. Only two of these nine neonates presented with hemorrhagic syndromes (two, petechial purpura; one, intracranial bleeding). The frequency of neonatal thrombocytopenia was higher in mothers with deep thrombocytopenia and in those who had not responded to corticosteroid treatment following diagnosis. No prognostic value could be assigned to the other maternal characteristics studied, such as a history of splenectomy, maternal treatment at the time of delivery, or the presence of platelet autoantibodies evaluated either with the platelet immunofluorescence test or the platelet Western blot immunoassay.

Neonatal alloimmune thrombocytopenic purpura.

We reviewed 58 literature reports of neonatal alloimmune thrombocytopenic purpura (NAITP). The mortality rate was 9%. The total incidence of suspected intracranial hemorrhage was 28%. We reviewed 17 sibship cases for the relation of birth order to treatment and outcome. Among firstborn affected infants (n = 17) the mortality rate and incidence of central nervous system sequelae were 24 and 47%, respectively, compared to rates of 5 and 15%, respectively, in their younger affected siblings (n = 20). The improved outcome in the latter group appeared to be related to more frequent cesarean section delivery and more frequent and earlier use of corticosteroids and maternal platelet transfusions in the neonate. Sensitive assays of maternal platelet alloantibody are now available, but they lack specificity for NAITP affecting the current gestation. There are two reports in which sensitive assays revealed rising titers of maternal platelet alloantibody during advancing gestation. We propose further study to determine if this is specific for the antepartum diagnosis of NAITP.

Successful renal transplantation for Epstein syndrome.

Successful cadaveric renal transplantation was accomplished in a patient with Epstein syndrome, a triad of macrothrombocytopenia, partial high-frequency hearing loss, and nephritis, which often progresses to complete renal failure. The success of the transplant demonstrates that the macrothrombocytopenia which occurs in this syndrome is not a contraindication to aggressive management of end-stage renal disease.