- Criggler-Najjar (CJ) Syndrome is characterized by the development of an unconjugated hyperbilirubinemia due to a hereditary mutations in UGT1A1, the enzyme which conjugates bilirubin to Glucuronic Acid (See: Heme Degradation). Two subtypes of the disease, CJ I and CJ II, have been described based on the severity of enzymatic deficiency.
|Criggler-Najjar Type I (CJ I)|
- Criggler-Najjar Type I is characterized by complete absence of UGT1A1 and thus an absolute inability to generate conjugated bilirubin. Consequently neonates with CJ I display extreme unconjugated hyperbilirubinemia which in the absence of appropriate therapy deposits in the CNS causing kernicterus and ultimately fatality.
|Criggerl-Najjar Type II (CJ II)|
- Criggler-Najjar Type II is characterized by a defect in UGT1A1 which reduces but does not totally eliminate its capacity for bilirubin conjugation. Although sufficient unconjugated hyperbilirubinemia arises to result in jaundice, enough bilirubin is conjugated to avoid kernicterus and death.