![]() At the extreme end of the spectrum, as already mentioned, kernicterus has been described. In contrast to the above-mentioned studies, a study from Israel found that 52% of 164 DAT-positive, ABO-incompatible newborns developed a TB >95th percentile, many of these within the first 24 hours. Despite this apparent clinical mildness, newborns with severe hyperbilirubinemia of early onset who do not respond to phototherapy and require intravenous immune globulin (IVIG) therapy or exchange transfusion are occasionally encountered. In one study, only 20% of DAT-positive neonates actually developed TB levels greater than 12.8 mg/dL (219 µmol/L) whereas, in another study, only 19.6% required phototherapy. 133 Not all DAT-positive neonates, however, develop severe hyperbilirubinemia. 134 Strength of DAT may also be predictive: ABO-heterospecific neonates with ++ DAT had a higher incidence of hyperbilirubinemia and higher COHbc values than those with ± or + DAT. 239,255 In one study, those infants who developed hyperbilirubinemia (TB >95th percentile on the Bhutani nomogram) had even higher COHb values than the already high values of those who were nonhyperbilirubinemic. Measurements of endogenous formation of CO, reflective of heme catabolism, have demonstrated, overall, an increased rate of heme catabolism in affected infants compared with controls. After delivery, there is a potential danger of hyperbilirubinemia.Ībout one-third of blood group A or B neonates born to a blood group O mother will have a positive direct Coombs' test. Infants may sometimes be born with moderate anemia. However, unlike the Rh situation, there is little danger of severe hyperbilirubinemia, anemia, or hydrops in utero, and prenatal intervention is not indicated. As with Rh isoimmunization, the immune process may commence in utero. Extravascular hemolysis of the IgG-coated RBCs is thought to be mediated within the reticuloendothelial system by Fc-receptor-bearing cells. Attachment to corresponding fetal RBCs may follow, provided these cells have the A or B antigen. In contradistinction to blood group A or B individuals, in whom their respective anti-B or anti-A antibodies are IgM molecules with limited ability to cross the placenta, the respective antibodies of blood group O individuals are predominantly smaller IgG molecules and may cross the placenta. This contrasts to Rh isoimmunization, in which immune sensitization occurs progressively with subsequent pregnancies. High titers of anti-A or anti-B antibodies can sometimes be found in blood group O women even before their first pregnancy. In some instances, women with blood group O have a high titer of naturally occurring anti-A or anti-B antibodies. 35,122,173,204,242,292,294ĪBO blood group heterospecificity is the situation in which a blood group A or B infant is born to a group O mother, a setup occurring in about 12% of pregnancies. ![]() In recent series of infants with either bilirubin encephalopathy/kernicterus or extreme hyperbilirubinemia reported from diverse countries including the United States, Canada, the United Kingdom, Ireland, Denmark, Switzerland, China, and Nigeria, in whom the etiology of the hyperbilirubinemia was determined, infants with blood group A or B born to group O mothers comprised 19% to 55%. The clinical picture is usually milder than that of Rh disease, although infrequently severe hemolysis with hyperbilirubinemia may occur. With the reduction of the incidence of Rh isoimmunization by immune prophylaxis, DAT-positive ABO incompatibility in industrialized countries with functional medical systems is now the single most prominent cause of immune hemolytic disease in the neonate. Martin MBBS, FRACP, in Fanaroff and Martin's Neonatal-Perinatal Medicine, 2020 ABO Heterospecificity.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |