Jaundice, also known as icterus, is a yellow pigmentation of the skin which is caused by high blood bilirubin levels (i.e. hyperbilirubinemia). Bilirubin is a natural yellow pigment produce by the breakdown from the red blood cells. Bilirubin circulates in the blood in the unconjugated form, which is then conjugated in the liver. The conjugation allows the transformation of a water-insoluble molecule in a water-soluble one, from unconjugated bilirubin to conjugated bilirubin, which can then be excreted in the bile.
Hyperbilirubinemia is a frequent disease after birth and occurs in 60 to 70% of term newborns and nearly all of preterm ones. Neonatal hyperbilirubinemia occurs in neonates because there is an imbalance between increased production and decreased elimination of bilirubin related to a temporarily impaired conjugation system of the liver.
The goal of the therapy is to decrease the level of the circulating unconjugated bilirubin or at least keeping it from increasing. Light in the range of approximately 400 to 500 nm with a peak at 460 nm is considered the most effective and is the standard treatment for neonatal Hyperbilirubinemia.
The interaction of blue light with bilirubin causes a photochemical change which transform unconjugated bilirubin into a water-soluble product that can be eliminated without the liver conjugation step.
Level of Bilirubin must be monitored as uncontrolled level of bilirubin can have severe consequences due to the toxicity of the bilirubin to brain (brainstem and basal ganglion); it can cause Kernicterus, or bilirubin encephalopathy, leading to devastating and permanent brain damages.