Which physical findings are characteristic of hemolytic disease of the newborn (HDN)?

Updated: Dec 28, 2017
  • Author: Sameer Wagle, MBBS, MD; Chief Editor: Muhammad Aslam, MD  more...
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An infant born to an alloimmunized mother shows clinical signs based on the severity of the disease. The typical diagnostic findings are jaundice, pallor, hepatosplenomegaly, and fetal hydrops in severe cases. The jaundice typically manifests at birth or in the first 24 hours after birth with rapidly rising unconjugated bilirubin level. Occasionally, conjugated hyperbilirubinemia is present because of placental or hepatic dysfunction in those infants with severe hemolytic disease. Anemia is most often due to destruction of antibody-coated red blood cells by the reticuloendothelial system, and, in some infants, anemia is due to intravascular destruction. The suppression of erythropoiesis by intravascular transfusion (IVT) of adult Hb to an anemic fetus can also cause anemia. Extramedullary hematopoiesis can lead to hepatosplenomegaly, portal hypertension, and ascites.

Anemia is not the only cause of hydrops. Excessive hepatic extramedullary hematopoiesis causes portal and umbilical venous obstruction and diminished placental perfusion because of edema. Increased placental weight and edema of chorionic villi interfere with placental transport. Fetal hydrops results from fetal hypoxia, anemia, congestive cardiac failure, and hypoproteinemia secondary to hepatic dysfunction. Commonly, hydrops is not observed until the Hb level drops below approximately 4 g/dL (Hct < 15%). [8]  Clinically significant jaundice occurs in as many as 20% of ABO-incompatible infants.

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