neonatal jaundice
Summary
Neonatal jaundice is yellowish discoloration of the skin and sclera in newborns due to elevated unconjugated (or sometimes conjugated) bilirubin, occurring in up to 60% of term and 80% of preterm infants. It is often physiologic due to immature hepatic conjugation and increased RBC turnover, but pathologic causes must be excluded to prevent kernicterus.
Detail
Neonatal jaundice results from an imbalance between bilirubin production and elimination. Physiologic jaundice appears after 24 hours of life, peaks around day 3-5, and resolves by 1-2 weeks; it results from increased bilirubin load (higher hematocrit, shorter RBC lifespan) combined with immature UDP-glucuronosyltransferase (UGT1A1) activity, which is required for bilirubin conjugation. Pathologic causes include hemolytic disease (Rh/ABO incompatibility, G6PD deficiency, hereditary spherocytosis), Crigler-Najjar syndrome (severe UGT1A1 deficiency), Gilbert syndrome (mild UGT1A1 deficiency), breast milk jaundice (due to glucuronidase in breast milk deconjugating bilirubin, peaks at 2 weeks), breastfeeding jaundice (inadequate intake causing dehydration and reduced bilirubin excretion), biliary atresia (conjugated hyperbilirubinemia presenting with pale stools/dark urine), and sepsis. Jaundice appearing within the first 24 hours is always pathologic and requires urgent workup, most commonly due to hemolysis. Bilirubin follows a cephalocaudal progression (face first, then trunk, then extremities), which can be used clinically to estimate severity.
The major clinical concern is unconjugated bilirubin crossing the blood-brain barrier, causing acute bilirubin encephalopathy and, if untreated, kernicterus—permanent neurologic damage affecting the basal ganglia, presenting with hypotonia, poor feeding, high-pitched cry progressing to hypertonia, opisthotonos, seizures, and later choreoathetoid cerebral palsy, sensorineural hearing loss, and gaze palsies. Total serum bilirubin should be plotted on hour-specific nomograms (Bhutani) to guide management. Treatment includes phototherapy (converts bilirubin to water-soluble lumirubin for excretion), and in severe cases, exchange transfusion. Direct (conjugated) hyperbilirubinemia is always pathologic and requires evaluation for biliary atresia, neonatal hepatitis, or metabolic disease, as it does not cause kernicterus but signals hepatobiliary dysfunction.
Sources
- First Aid for the USMLE Step 1
- Nelson Textbook of Pediatrics
- UpToDate: Unconjugated hyperbilirubinemia in term and late preterm infants
- Robbins Basic Pathology
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