Pathogenesis and Phases of HDFN

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Questions and Answers

What is the most likely cause of severe long-term neurological impairment in children treated with intrauterine transfusion (IUT)?

Incomplete maternal antibody decay (correct)

Rapid maternal antibody decay

Excessive fetal iron accumulation

Increased maternal RBC production

What is the main reason for the decrease in the rate of RBC destruction after birth?

Absence of maternal antibodies (correct)

Increased hemoglobin levels

Production of fetal antibodies

Enhanced erythropoiesis

What is the half-life of IgG in the infant's circulation?

30 days

10 days

20 days

25 days (correct)

Which type of anemia is characterized as occurring within 7 days of birth?

Early hemolytic anemia Signup and view all the answers

What contributes to late hypo regenerative anemia in affected newborns?

Erythropoietin deficiency Signup and view all the answers

What causes neonatal jaundice after birth?

An inefficient metabolism of bilirubin by the immature liver Signup and view all the answers

What is the significance of the Direct Antiglobulin Test (DAT) in diagnosing ABO HDFN?

It is the most important diagnostic test for evaluating jaundice Signup and view all the answers

What Hb level indicates a need for cordocentesis blood sample?

Less than 10 g/dL Signup and view all the answers

What can untreated high bilirubinemia lead to in neonates?

Kernicterus or permanent brain damage Signup and view all the answers

What is the initial intrauterine transfusion typically repeated to manage?

Maintain fetal hemoglobin above 10 g/dL Signup and view all the answers

Which test can show a positive result even in the absence of clinical anemia in newborns?

Direct Antiglobulin Test (DAT) Signup and view all the answers

What is a recommended procedure for collecting cord blood samples?

Collect by venipuncture to avoid contamination Signup and view all the answers

Which of the following characteristics is not typical for RBCs used in intrauterine transfusions?

Hemoglobin S positive Signup and view all the answers

What is a significant risk associated with cordocentesis and intrauterine transfusion?

Increased antibody production in the mother Signup and view all the answers

What should be investigated if the DAT result is negative but the infant is jaundiced?

Other causes of jaundice Signup and view all the answers

What type of bilirubin is found in excess leading to neonatal jaundice?

Indirect (unconjugated) bilirubin Signup and view all the answers

What best describes the potential outcomes for children treated with intrauterine transfusion?

Low rates of neurocognitive impairment when not severely hydropic Signup and view all the answers

What is the recommended frequency for repeating intrauterine transfusions until delivery?

Every 2 to 4 weeks Signup and view all the answers

What happens to hemoglobin released from RBC destruction during the neonatal period?

It is metabolized to bilirubin at different stages Signup and view all the answers

Which factor can complicate the search for RBCs for intrauterine transfusion?

High-level antigen matching Signup and view all the answers

What is the chance of adverse fetal events when performing intrauterine transfusion alone?

Between 1% and 3% Signup and view all the answers

What should be monitored after a two-volume exchange transfusion?

Platelet count Signup and view all the answers

What is the purpose of phototherapy in newborns?

To metabolize unconjugated bilirubin Signup and view all the answers

Which treatment for hyperbilirubinemia reduces hemolysis caused by maternal antibodies?

Intravenous Immune Globulin (IVIG) Signup and view all the answers

What generally happens to the bilirubin levels after a two-volume exchange transfusion?

Decreases by 50% Signup and view all the answers

What characteristic must RBC units have for infants receiving top-off transfusions?

Have the same attributes as those noted with IUT and exchange transfusion Signup and view all the answers

Which of the following is a primary measure to prevent HDFN?

Dosing of RhIG Signup and view all the answers

Why should RhD negative RBCs be preserved in blood bank inventory?

To lower the risk of RhD sensitization in women of childbearing potential Signup and view all the answers

What is not affected by the use of IVIG?

Need for top-off transfusions Signup and view all the answers

What test is used to quantify fetal cells in maternal blood?

Kleihauer-Betke test Signup and view all the answers

What is the role of maternal blood volume in calculating fetomaternal hemorrhage?

It is the denominator in the calculation formula. Signup and view all the answers

What defines Weak D phenotypes in RhD typing?

Inaccurate detection of RhD type due to genetic variations. Signup and view all the answers

How many vials of RhIG are required after calculating the fetomaternal hemorrhage volume?

Calculated volume plus one vial. Signup and view all the answers

Which assay may provide more accurate quantitation of fetomaternal hemorrhage compared to Kleihauer-Betke?

Flow cytometry Signup and view all the answers

In what time frame should additional vials of RhIG be administered after delivery if necessary?

Within 72 hours. Signup and view all the answers

Which of the following is NOT considered a cause of differential diagnosis related to blood disorders?

Nutritional anemia Signup and view all the answers

What characterizes the fetal cells during the Kleihauer-Betke test?

They remain pink after acid treatment. Signup and view all the answers

Study Notes

Pathogenesis of HDFN

IgG antibodies are responsible for RBC destruction in HDFN
IgG crosses the placenta and binds to fetal RBCs
Maternal antibodies persist in newborn infant's circulation after birth
Antibody-mediated hemolysis continues for several days or weeks after delivery

Phases of Anemia in HDFN

Early hemolytic anemia: Occurs within 7 days of birth
Late hemolytic anemia: Occurs 2 weeks or more after birth
Late hyporegenerative anemia: Associated with transfusions and IU
- Marrow suppression due to antibody destruction of RBC precursors and erythropoietin deficiency

Neonatal Manifestations of HDFN-Induced Anemia

Severity of anemia varies depending on the time of onset
Infants with severe anemia are more likely to have long-term neurological impairment

Bilirubin

Hemoglobin is metabolized to bilirubin after RBC destruction.
Unconjugated bilirubin is water-insoluble and transported to the liver to be conjugated and excreted.
Infant liver's inability to efficiently metabolize bilirubin can lead to unconjugated bilirubin accumulation and neonatal jaundice.
High bilirubin levels can cause kernicterus, leading to permanent brain damage.

Postnatal Diagnosis of HDFN

No single serologic test is diagnostic for ABO HDFN
Direct antiglobulin test (DAT) on cord or neonatal RBCs is crucial
DAT can be positive even in the absence of clinical anemia.
Cord blood samples should be collected by venipuncture to avoid maternal blood contamination

Intrauterine Transfusion (IUT)

Goal of IUT is to maintain fetal hemoglobin above 10 g/dL.
IUT is typically repeated every 2 to 4 weeks until delivery.
Initial IUT is rarely performed after 36 weeks' gestation.
IUT carries risks including infection, premature labor, and placental trauma
High-level antigen matching may reduce the risk of further alloimmunization, but finding compatible RBCs is challenging.
Despite risks, children treated with IUT have a relatively low rate of neurocognitive impairment if they were not severely hydropic.

Exchange Transfusion

Replaces infant's blood with RBC unit mixed with plasma to create reconstituted whole blood.
Reduces bilirubin levels
Monitoring for iatrogenic thrombocytopenia is essential after the procedure.

Simple Transfusions

Small-volume or 'top-off' RBC transfusions used to correct anemia.
Infants should be monitored for clinical signs of anemia.
RBCs used for transfusion have similar attributes as those used for IUT and exchange transfusion.

Phototherapy

Used to metabolize unconjugated bilirubin to isomers less lipophilic and less toxic to the brain.
Effective for infants with mild to moderate hemolysis.

Intravenous Immune Globulin (IVIG)

Treats hyperbilirubinemia of the newborn caused by HDFN.
IVIG competes with maternal antibodies for Fc receptors on macrophages, reducing hemolysis.
May reduce the need for transfusions, but does not affect the need for top-off transfusions.

Prevention of HDFN

RhD negative RBCs should be reserved for women of childbearing potential.
Matching minor blood group antigens is recommended for women of childbearing potential
K-negative RBC units should be used for women younger than 45-50 years of age.
Kleihauer-Betke test is used to estimate fetal-maternal hemorrhage (FMH) volume
Flow cytometry provides more accurate quantification of FMH volume.
RhD genetic testing is encouraged for patients with a weak D phenotype.

Differential Diagnosis

RBC enzyme disorders (e.g., G6PD deficiency)
Disorders of hemoglobin synthesis (e.g., alpha-thalassemias)
RBC membrane abnormalities (e.g., hereditary spherocytosis)
Hemangiomas (Kasabach–Merritt syndrome)
Acquired conditions (e.g., sepsis, TORCH infections)

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Description

This quiz explores the pathogenesis of Hemolytic Disease of the Fetus and Newborn (HDFN), focusing on how IgG antibodies lead to RBC destruction. It details the phases of anemia in HDFN, neonatal manifestations, and the role of bilirubin metabolism. Test your understanding of this critical topic in neonatal care!