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Crigler-Najjar Syndrome or CNS is a rare disorder affecting the metabolism of bilirubin, a chemical formed from the breakdown of blood. The disorder results in an inherited form of non-hemolytic jaundice, often leading to brain damage in infants.
This syndrome is divided into two types: type I and type II, which is sometimes called Arias syndrome. These two types, along with Gilbert’s syndrome,Dubin-Johnson syndrome, and Rotor syndrome, make up the five known hereditary defects in bilirubin metabolism. Unlike Gilbert’s syndrome, only a few hundred cases of CNS are known to exist.
This is a very rare disease (estimated at 0.6 – 1.0 per million live births), and consanguinity increases the risk of this condition (other rare diseases may also be present). Inheritance is autosomal recessive.
Intense jaundice appears in the first days of life and persists thereafter. Type 1 is characterised by a serum bilirubin usually above 345 µmol/L (310 – 755) (whereas the reference range for total bilirubin is 2 – 14 µmol/L).
No UGT1A1 (UDP glucuronosyltransferase 1 family, polypeptide A1) expression can be detected in the hepatic tissue. Hence, there is no response to treatment with phenobarbital[1] (which causes enzyme induction). Most patients (type IA) have a mutation in one of the common exons (2 to 5), and have difficulties conjugating several additional substrates (several drugs and xenobiotics). A smaller percentage of patients (type IB) have mutations limited to the bilirubin-specific A1 exon; their conjugation defect is mostly restricted to bilirubin itself.
Prior to the availability of phototherapy, these children died of kernicterus (=bilirubin encephalopathy), or survived until early adulthood with clear neurological impairment. Today, therapy includes
Differs from type I in several aspects:
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