Hence, there is no response to treatment with phenobarbital, which causes CYP450 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. Before the availability of phototherapy, these children died of kernicterus (bilirubin encephalopathy) or survived until early adulthood with clear neurological impairment. Today, therapy includes

exchange transfusions in the immediate neonatal period
12 hours/day phototherapy
heme oxygenase inhibitors to reduce transient worsening of hyperbilirubinemia (although the effect of the drug decreases over time)
oral calcium phosphate and carbonate to form complexes with bilirubin in the gut
liver transplantation before the onset of brain damage and before phototherapy becomes ineffective at later age

Type II
The inheritance patterns of both Crigler–Najjar syndrome types I and II are autosomal recessive.However, type II differs from type I in a number of different aspects:

Bilirubin levels are generally below 345 μmol/L [20 mg/dL] (range 100–430 μmol/L [6–24 mg/dL]; thus, overlap may sometimes occur), and some cases are only detected later in life. Because of lower serum bilirubin, kernicterus is rare in type II. Bile is pigmented, instead of pale in type I or dark as normal, and monoconjugates constitute the largest fraction of bile conjugates. UGT1A1 is present at reduced but detectable levels (typically <10% of normal), because of single base pair mutations.
Since only one enzyme is working improperly, gene therapy for Crigler-Najjar is a theoretical option which is being investigated. Eponym
The condition is named for John Fielding Crigler (1919 – May 13, 2018), an American pediatrician and Victor Assad Najjar (1914–2002), a Lebanese-American pediatrician. References
External links

Crigler–Najjar syndrome, type 1 at NIHs Office of Rare Diseases
Crigler–Najjar syndrome, type 2 at NIHs Office of Rare Diseases