Definition of Hyperbilirubinemia type I

Hyperbilirubinemia type I: Better known as Gilbert's disease, a common but harmless genetic condition in which a liver enzyme essential to the disposal of bilirubin (the chemical that results from the normal breakdown of hemoglobin from red blood cells) is abnormal. (The errant enzyme is called UDP- glucuronosyltransferase).

This enzyme abnormality results in mild elevation of bilirubin pigment in the blood and the elevated bilirubin pigment, in turn, can sometimes cause mild yellowing (jaundice) of the eyes. People with Gilbert's disease are otherwise entirely normal with no other signs or symptoms and their liver enzymes in blood serum are also entirely normal.

The gene for Gilbert's disease has been mapped a non-sex chromosome (chromosome 2). A single dose of the Gilbert gene is sufficient to produce the disease. (The diseases is said therefore to be an autosomal dominant trait). If someone has Gilbert's disease, the chance of their transmitting the Gilbert gene to each of their children is one-half (50%) and each child who gets the gene gets Gilbert's disease.

There is no need for treatment in Gilbert's disease, and the prognosis (outlook) is excellent.

Gilbert's syndrome is a frequent finding in people in the United States and Europe. The condition is usually detected serendipitously (purely by accident) in the course of routine blood screening. Gilbert's disease is thus an accidentally-encountered enzyme abnormality of no health consequence.