Pediatrics Dec 2020 Flashcards
What are the 2 type incompatibility to cause HDNB?
Rh and ABO incompatibility
What is more likely to cause significant Hemolytic Disease of the Newborn – Rh Incompatibility or ABO?
- RhD is most potent immunogen of red blood cell (RBC) antigens
- Low rates of ABO alloimmunization despite relatively high rates of ABO incompatibility can be explained by ABO antibodies being predominantly immunoglobulin M class, an antibody class not effectively transported across the placenta
- ABO incompatibility occurs in approximately 15% of all pregnancies but results in hemolytic disease in only 3% of newborns, with less than 0.1% of infants needing exchange transfusion
In what scenario is it more likely that a newborn develop HDNB from ABO incompatibility?
ABO incompatibility occurs in approximately 15% of all pregnancies but results in hemolytic disease in only 3% of newborns, with less than 0.1% of infants needing exchange transfusion
Hemolysis caused by ABO incompatibility is usually seen in newborns with blood type A or B born to blood type O mothers.
Expected lab work of newborn with hyperbilirubinemia due to ABO incompatibility?
Hemolysis caused by ABO incompatibility is usually seen in newborns with blood type A or B born to blood type O mothers.
Laboratory findings include a WEAKLY positive direct Coombs test, high reticulocyte count, spherocytes on blood smear, and high levels of unconjugated bilirubin.
Framework Question:
In evaluation “newborn” with jaundice, what is a good way to categorize the differential diagnosis of the possible causes?
By pathophysiology:
- Increased RBC turnover
- Decreased uptake and conjugation (liver)
- Increased enterohepatic uptake
Increased turn over/lysis of red blood cells
- Isoimmunization (Rh, ABO and minor blood groups)
RBC enzyme defects (G6PD deficiency, pyruvate kinase deficiency)
- RBC structural abnormalities (hereditary spherocytosis)
- Cephalohematoma or bruising
- Polycythemia
- Infection (sepsis or UTI)
Decreased uptake and conjugation (liver)
- Gilbert syndrome, Crigler-Najjar syndrome
- Congenital hypothyroidism
- Breast milk jaundice (resulting from inhibition of glucuronyl transferase activity)
- Immature glucuronyl transferase activity
Increased enterohepatic reabsorption
- Breastfeeding jaundice (caused by limited milk supply in the first days after birth)
- NPO
- Bowel obstruction
What is the cause of physiologic jaundice in most newborns?
Most physiologic jaundice in full-term neonates is the result of a combination of these causes (ie, increased heme catabolism, immature glucuronyl transferase activity resulting in diminished conjugation, and increased enterohepatic circulation resulting from limited oral intake in the first days after birth
Degradation of red blood cells releases hemoglobin, which is converted to bilirubin by macrophages in the liver and spleen and released into the plasma. Bilirubin is then bound to serumalbuminand transferred to the liver, where it is conjugated to glucuronate via glucuronyl transferase
How common is physiologic jaundice of the newborn?
60%
What distinguished physiologic vs pathologic jaundice when evaluating the newborn?
Jaundice > 24 hours (vs <24 hours)
Peak bili at 4-5 days (5-7 days for preterm) (vs precipitous rise)
And resolution within 14 days ( > 14 days for resolution)
Normal conjugated bili (vs. elevated conjugated bili)
Tip: notice the first 3 has to do with the natural history of jaundice – onset, peak and resolution
Vs.
Pathologic
What is the key difference in distinguishing breast milk jaundice vs breast feeding jaundice? Explain the difference in how they contribute to jaundice in the newborn?
Timing:
- <5 days is likely breastfeeding jaundice
- > 5 days is breast milk jaundice
Tip:
Breast feeding jaundice is really “breast non-feeding jaundice” or “not enough breast feeding jaundice” is due to dehydration and the enterohepatic reabsorption of bilirubin
Breast milk jaundice is a matter of the breast milk itself, inhibiting
