Physiology of Jaundice
What pigment builds up in neonatal jaundice?
Bilirubin (unconjugated or conjugated)
Jaundice appearing after 24 hrs, peaking at day 3–5, and resolving by 1 week in term infants is called?
Physiologic jaundice
Jaundice before what time cutoff is always pathologic?
Before 24 hrs
What is the mainstay of treatment for significant unconjugated hyperbilirubinemia?
Phototherapy
Why do preterm babies have a higher risk of severe jaundice?
Even more immature conjugation + less albumin binding
Why do newborns have higher bilirubin production than adults?
Higher RBC turnover & shorter lifespan (90 days)
Breastfeeding jaundice is due to what mechanism?
Inadequate intake → dehydration & ↓ elimination of bilirubin
Direct hyperbilirubinemia is always concerning. What is the threshold for concern?
Direct >1 mg/dL if total <5, or >20% of total bilirubin
What wavelength/color of light is used in phototherapy?
Blue light (460–490 nm)
Why don’t you see kernicterus with conjugated hyperbilirubinemia?
Conjugated bilirubin is water-soluble and cannot cross the BBB
What enzyme is immature in the neonatal liver, limiting bilirubin conjugation?
UDP-glucuronyl transferase
Breast milk jaundice (different from breastfeeding jaundice) is due to what?
Substances in breast milk inhibit conjugation (β-glucuronidase)
Name one hemolytic disease that can cause early jaundice
ABO incompatibility or Rh incompatibility
When is exchange transfusion indicated?
When bilirubin is dangerously high or not responsive to phototherapy
What antibiotic displaces bilirubin from albumin, raising kernicterus risk?
Sulfonamides
What protein normally binds unconjugated bilirubin in the blood?
Albumin
Jaundice appearing in the first 24 hrs of life is always what?
Pathologic
Pale stools and dark urine in a jaundiced infant suggest what diagnosis?
Biliary atresia
What tool is used to decide if a baby’s bilirubin is at treatment threshold?
Bhutani nomogram (or AAP guidelines)
Which enzyme deficiency can cause neonatal hemolytic jaundice that may be triggered by oxidative stress, such as infection or certain drugs?
G6PD deficiency
What serious complication can result if unconjugated bilirubin crosses the BBB?
Kernicterus
What type of bilirubin is elevated in biliary atresia?
Conjugated (direct) bilirubin
Lethargy, poor tone, and high-pitched cry in a jaundiced infant suggest what?
Acute bilirubin encephalopathy
In breast milk jaundice, should breastfeeding be stopped?
No, continue breastfeeding
What’s the “double whammy” baby at risk: which 2 risk factors together are highest risk for severe jaundice?
Prematurity + hemolysis (e.g., Rh incompatibility)