Jaundice

Jaundice is yellowing of the skin and whites of the eyes caused by elevated bilirubin in the blood. It can result from increased bilirubin production, impaired liver processing, or blocked bile flow.

Bilirubin: A yellow pigment formed mainly when the body breaks down heme from aging red blood cells. Its accumulation in blood produces the characteristic yellow discoloration.
Neonatal jaundice: Jaundice in a newborn, commonly caused by temporary immaturity of bilirubin processing. It is a frequent, age-specific form with risks and treatment thresholds of its own.
Hyperbilirubinemia: An abnormally high concentration of bilirubin in the blood. It is the biochemical abnormality underlying visible jaundice.
Kernicterus: Permanent neurological injury caused by bilirubin deposition in the brain, usually after severe neonatal hyperbilirubinemia. It is the devastating consequence clinicians seek to prevent in newborn jaundice.
Carotenemia: Yellow-orange skin discoloration caused by carotene accumulation, typically sparing the whites of the eyes. It resembles jaundice but does not result from elevated bilirubin.
Heme catabolism: The breakdown of heme into biliverdin and then bilirubin, principally in macrophages. Excessive breakdown of red blood cells can raise bilirubin before it reaches the liver.
Hemolytic anemia: Anemia caused by red blood cells being destroyed faster than the body can replace them. Accelerated red-cell destruction can overwhelm bilirubin clearance and cause jaundice.
Unconjugated bilirubin: Bilirubin before liver conjugation; it circulates largely bound to albumin and is not water-soluble. This form rises with excess production or impaired hepatic uptake and conjugation.
Acute bilirubin encephalopathy: Acute neurological dysfunction caused by bilirubin toxicity in a newborn’s brain. Early signs can precede permanent injury from severe neonatal hyperbilirubinemia.
Pseudojaundice: Yellow discoloration resembling jaundice that occurs without elevated bilirubin. It distinguishes visible yellowing from bilirubin-driven discoloration.

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