Sorted By Test Name - Mayo Medical Laboratories

UGT2
89611
II; CN type I does not respond to phenobarbital treatment. If left untreated, the buildup of bilirubin in a
newborn can cause kernicterus, bilirubin-induced brain damage. Treatments of CN include: phototherapy,
heme oxygenase inhibitors, oral calcium phosphate and carbonate, and liver transplantation. Phototherapy
becomes ineffective at later ages and liver transplantation should occur prior to the onset of brain damage
(before phototherapy becomes ineffective). The UGT1A1 gene maps to chromosome 2q37 and contains 5
exons. Currently, there are more than 130 known mutations in UGT1A1, with 45 mutations that cause a
decrease in UGT1A1 enzyme activity. Analysis is performed for the familial mutation only.
Useful For: Identifying the presence of a UGT1A1 mutation when the mutation has been identified in a
family member (carrier or affected)
Interpretation: An interpretive report will be provided.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Guilemette C: Pharmacogenomics of human UDP-glucuronosyltransferase
enzymes. Pharmacogenomics J 2003;3:136-158 2. Innocenti F, Grimsley C, Das S, et al: Haplotype
structure of the UDP-glucuronosyltransferase 1A1 promoter in different ethnic groups. Pharmacogenetics
2002;12:725-733 3. Costa E, Vieira E, Martins M, et al: Analysis of the UDP-glucuronosyltransferase
gene in Portuguese patients with a clinical diagnosis of Gilbert and Crigler-Najjar syndromes. Blood Cells
Mol Dis 2006;36:91-97 4. Kitagawa C, Ando M, Ando Y, et al: Genetic polymorphism in the
Phenobarbital- responsive enhancer module of the UDP-glucuronosyltransferase 1A1 gene and irinotecan
toxicity. Pharmacogenet Genomics 2005;15:35-41
UDP-Glucuronosyl Transferase 1A1 (UGT1A1), Full Gene
Sequencing, Hyperbilirubinemia
Clinical Information: Bilirubin, resulting from the breakdown of heme, is a water-insoluble toxic
compound. Uridine diphosphate (UDP)-glycuronosyl transferase 1A1 (UGT1A1) is responsible for
bilirubin conjugation with glucuronic acid. This renders the bilirubin water soluble and permits excretion
of the bilirubin-glucuronide conjugates in urine.(1) Genetic mutations in the UGT1A1 gene may cause
reduced or absent UGT1A1 enzymatic activity resulting in hyperbilirubinemia (eg, Gilbert syndrome,
Crigler-Najjar). Gilbert syndrome, found in 5% to 10% of the population, is the most common hereditary
cause of increased bilirubin and is associated with mild hyperbilirubinemia (bilirubin levels are typically
around 3 mg/dL).(2) Gilbert syndrome is caused by a 25% to 50% reduced glucuronidation activity of the
UGT1A1 enzyme and characterized by episodes of mild intermittent jaundice and the absence of liver
disease. Crigler-Najjar (CN) types I and II are inherited causes of severe unconjugated
hyperbilirubinemia. CN type I is associated with no UGT1A1 enzymatic activity and usually presents as
intense jaundice in the first days of life and persists thereafter.(3) Type II is a milder form in which
bilirubin levels are