Jaundice, also known as hyperbilirubinemia, is a yellow discoloration of the body tissue resulting from the accumulation of an excess of bilirubin. Deposition of bilirubin happens only when there is an excess of bilirubin, a sign of increased production or impaired excretion. The normal serum levels of bilirubin are less than 1mg/dl; however, the clinical presentation of jaundice as scleral icterus (peripheral yellowing of the eye sclera), is best appreciated only when the levels reach more than 3 mg/dl. Sclerae have a high affinity for bilirubin due to their high elastin content. With further increase in serum bilirubin levels, the skin will progressively discolor ranging from lemon yellow to apple green, especially if the process is long-standing; the green color is due to biliverdin.
Bilirubin has two components: unconjugated(indirect) and conjugated(direct), and hence elevation of any of these can result in jaundice. Icterus acts as an essential clinical indicator for liver disease, apart from various other insults.
Yellowing of skin sparing the sclerae is indicative of carotenoderma which occurs in healthy individuals who consume excessive carotene-rich foods.