This is an extremely rare disease that is inherited in an autosomal recessive pattern.
This enzyme is responsible for processing unconjugated, lipid-soluble bilirubin into conjugated, water-soluble bilirubin that can be excreted. Unlike Gilbert’s disease in which a patient still retains some enzymatic function, there is total lack of this enzyme in Crigler-Najjar type I so unconjugated bilirubin quickly rises to toxic levels.
Due to highly elevated bilirubin at birth and the inability to excrete it, neonates will have persistent jaundice within a few days of life.
Because excess unconjugated bilirubin is lipid-soluble, it can cross the blood-brain-barrier (BBB) and deposit in the gray matter, causing permanent CNS damage. Kernicterus results in poor growth and development and is the most common cause of death in Crigler-Najjar type I.
Liver enzymes such as AST and ALT are not typically affected in this disease.
Bilirubin levels are usually in the range of 20-25 mg/dL, but may reach up to 50 mg/dL in Crigler-Najjar type I. Both Crigler-Najjar type I and Gilbert’s syndrome show elevated levels of unconjugated bilirubin, which serves to contrast them from Dubin-Johnson or Rotor syndrome that involve increased conjugated bilirubin levels. Stool color will be normal.
When neonatal skin is exposed to certain wavelengths of fluorescent light, it accelerates the conversion process of unconjugated bilirubin into an excretable form. The jaundiced infant is exposed to phototherapy lamps for up to 12 hrs/day.
Similar to dialysis in which whole blood is removed from the body, filtered and cleaned by a machine, and returned to the patient, plasmapheresis filters plasma only and can rapidly remove undesirable substances bound to albumin, such as unconjugated bilirubin.
Calcium phosphate is given orally and works by binding bilirubin in the GI tract to prevent reabsorption and assist excretion; it is best used in conjunction with phototherapy. Orlistat is a lipase inhibitor that decreases absorption of fats in the GI tract; since unconjugated bilirubin is lipid-soluble, less fat absorption means less bilirubin absorption and increased excretion.
Unless a patient is rapidly diagnosed and treated with the above mentioned therapies, these patients will die before the age of two due to the irreversible CNS effects of kernicterus. The only definitive long-term treatment is liver transplant.
Crigler-Najjar syndrome, type II, also called Arias syndrome, is distinct from type I because these patients still retain some functioning UDP-glucuronosyltransferase enzymes. The two types can be distinguished by administering phenobarbital, a barbiturate and P450 inducer that increases liver enzyme synthesis. With type II, unconjugated bilirubin levels will decrease as the remaining enzymes are increased after administration of phenobarbital. Unconjugated bilirubin levels remain elevated in type I disease, due to complete absence of the enzyme, as phenobarbital cannot increase the enzyme levels if they are not being made.
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