A neonate has ABO incompatibility. Peripheral smear will showaEUR'

Microspherocytes ABO incompatibilityis usually a mild hemolytic disease that causes mild to moderate anemia. Ilemolysis associated with ABO incompatibility exclusively occurs in type "0" mothers with fetuses who have type A or type B blood. - The naturally occurring antibodies in ABO blood group (A, B, AB) is of the "IgM class" and it cannot cross the placenta. - As compared with the other ABO blood groups that have predo- minantly IgM antibodies group 0 mothers also have significant amount of naturally occurring "IgG antibody". -These IgG antibodies can easily cross the placenta and produce hemolysis in,fetus. ABO incompatibility usually causes mild hemolysis and anemia. The lack of severity of hemolytic disease can be attributed to the following factors. - There is wide expression of A and B antigens not only on red cells but also in plasma and other cells which will paially neutralize maternally derived ABO antibodies. - In addition, fetal RBC's are not .fully developed in the infant and they express less number of A and B antigenic sites, hence the low incidence of significant hemolysis in affected neonates. Therefore in ABO incompatibility, hyperbilirubinemia is the predo- minaret manifestation of incompatibility (rather than anemia). The peripheral blood picture in these patients show Micro.spherocytesQ Reticulocytosis Polychromasia (not as characteristically seen as in other hemolytic anemias) Microspherocytes Spherocytes are associated with allt0i117177Une hemolytic anemias as the cell membrane of antibody coated RBC is lost .following interaction of RBC's with splenic macrophages. The slow. .flow of blood through the spleen provides an ample oppounity for the macrophage to come in contact with coated RBC's. The macrophages subsequently removes a poion of the RBC membrane and release the RBC in the spherocy- tic form with a typically decreased surface area to volume ratio. Note : Microspherocytes are characteristically seen in of ABO incompati- bility but in the other hemolytic disease of the newborn, i.e. erythroblastosis fetalis, they are characteristically absent. Polychromasia Polychromasia can be seen in ABO incompatibility but is not characteristic as in any other hemolytic anemia Polychromasia refers to variation in erythrocyte coloration - This variation is largely related to be maturation of the erythrocytes - The younger form owing to the presence of nucleus or RNA, stains blue, with Romanowsky stains where as mature forms due to the absence of nuclear material will stain uniformly orange pink. - Polychromasia is usually seen when RBC is released prematurely from the bone 111(1i-row to compensate for the blood loss. They are usually associated with hemolysis - In these conditions there is an increased erythroid response from the bone marrow - Immature RBC's or reticulocytes move into the circulation from the bone marrow. These RBC's have nucleus (if they are upto normoblast stage, or RNA's (as in reticulocytes) - These immature BBC's stain blue with Romanowsky stains. In ABO incompatibility in the newborn hemolysis is mild, the compensatory erythroid response from the bone marrow too would be mild. That means few immature RBC's move into the circulation from bone marrow therefore polychromasia is not so prominent.