Jaundice

Jaundice is a yellow tint of the skin, the whites of the eyes and moist linings such as the inside of the mouth. Also called icterus, it is a sign of an underlying problem, not a disease in itself. The color comes from bilirubin, a yellow-orange pigment made when the heme in hemoglobin from worn-out red blood cells is broken down. It usually shows first in the eyes, at blood levels of roughly 2 to 3 mg/dL.

Fresh, or unconjugated, bilirubin does not dissolve in water, so it travels bound to the protein albumin. Liver cells take it up, attach glucuronic acid so that it dissolves in water (conjugation) and send it out in bile to the intestine. Jaundice appears when this chain breaks. Prehepatic causes make too much bilirubin, as when red cells burst early in hemolytic anemia. Hepatic causes harm or slow liver cells, as in viral hepatitis, drug injury or inherited Gilbert syndrome. Posthepatic, or obstructive, causes block bile drainage, such as a gallstone or pancreatic tumor in the common bile duct.

The type of bilirubin raised hints at the cause. Conjugated bilirubin can enter urine, so liver and bile duct disease often bring dark urine, and pale stools when bile cannot reach the gut. Many newborns have brief, mild jaundice while their liver matures.