Hyperbilirubinemia Constitutional

**Constitutional hyperbilirubination** (HbC) is a genetically determined disorder of bilirubin metabolism in the blood, accompanied by a steady increase, despite normal hemolysis in the fetus in utero and in the newborn [1, 2].

**Physiology of constitutional hyperbilirubinomia**

The human body constantly synthesizes porphyrins, which are pigments that contribute to the color of the skin yellow. They are formed from glycine and the enzyme uroporphyrinogen synthase, which is part of the iron transport chain (ITC). In a healthy state, CPZ functions properly, resulting in the maintenance of normal levels of the pigment in the blood: bilirubin and its derivatives, such as free bilirubin (FB) and conjugated bilirubin. NB is typically utilized by the liver through a fermentation process without further pigment formation, and conjugation of NB with glucuronic acid allows excess pigment to be removed from the body before it is released back into the blood. This is important for maintaining the normal functioning of the body as a whole [3].

In HbC, there is a defect in the USF gene, which regulates the production of the enzyme UDP-glucuronosyltransferase. This leads to a deficiency of the enzyme responsible for the conjugation of bilirubin[4].

The P450 RIIA glycoprotein enzyme is the most important sulfhydroxylase enzyme system within