AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Crigler-Najjar syndrome (CNS) is a rare autosomal recessive disorder of bilirubin metabolism. Two distinct forms have been described, as follows: type 1 and type 2. Type 1 CNS, first described in 1952 by Crigler and Najjar, is associated with neonatal unconjugated hyperbilirubinemia (high levels) and kernicterus. Type 2 CNS (also called Arias syndrome), first described in 1962 by Arias, presents with a lower serum bilirubin level and responds to phenobarbital treatment.

The differential diagnosis of hyperbilirubinemia can be divided into 3 broad groups: (1) disorders of excessive bilirubin production (eg, hemolysis, ineffective erythropoiesis), (2) impaired hepatic handling of bilirubin (eg, hepatitis, cirrhosis, inherited syndromes), and (3) defective bile outflow (eg, intrahepatic or extrahepatic biliary obstruction).

A markedly elevated unconjugated (indirect) hyperbilirubinemia is observed in inherited disorders such as Gilbert syndrome and CNS. Among the inherited unconjugated hyperbilirubinemias, Gilbert syndrome is believed to affect approximately 3-7% of the adult population. CNS is a much rarer disorder, with only a few hundred cases described in the literature.

Pathophysiology

Effective elimination of bilirubin requires its conversion to polar derivatives. In humans, conjugation of bilirubin with the sugar molecule glucuronic acid accomplishes this conversion in a process called glucuronidation.

CNS is elicited by a lack or deficiency of the enzyme uridine diphosphate glycosyltransferase (UGT). Type 1 CNS is associated with an almost complete absence of the enzyme, which results in very high levels of unconjugated hyperbilirubinemia (up to 50 mg/dL) at birth. Lower levels of serum bilirubin (up to 20 mg/dL) and markedly depressed activity of hepatic UGT are characteristic of type 2 CNS (Arias syndrome). Importantly, treatment with phenobarbital can induce the expression of UGT in patients with type 2 CNS, with a decrease in the serum bilirubin level of approximately 25%.

CNS is caused by alterations in the coding sequence of UGT. This results in complete absence of UGT or the presence of abnormal UGT with reduced or no enzyme activity. In contrast, in Gilbert syndrome, the defect is in the promoter region of UGT, and reduced amounts of the normal protein are produced.

Frequency

United States

CNS is an extremely rare disorder that follows an autosomal recessive pattern of inheritance. Incidence is less than 1 case per 1,000,000 births. Only a few hundred cases have been described in the world literature, and the real prevalence is unknown.

Mortality/Morbidity

If left untreated, type 1 CNS is uniformly lethal secondary to the development of kernicterus by age 2 years. Although much rarer, bilirubin encephalopathy can also occur in type 2 CNS, usually when patients experience a superimposed infection or stress.

Race

CNS is thought to affect all races equally.

Sex

CNS occurs in both sexes equally.

Age

If left untreated, type 1 CNS is uniformly lethal secondary to the development of kernicterus by age 2 years. Although much rarer, bilirubin encephalopathy can also occur in type 2 CNS, usually when patients experience a superimposed infection or stress.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Because of its autosomal recessive transmission, consanguinity is a risk factor for CNS, especially type 1 CNS.

Physical

Persistent jaundice is present at or soon after birth in type 1 CNS. Jaundice may not manifest until later in infancy or childhood in type 2 CNS. Kernicterus is the most worrisome consequence of hyperbilirubinemia and occurs in virtually all patients with untreated type 1 CNS, especially in the first few days of life. Bilirubin encephalopathy is rare in patients with type 2 CNS, but it can be induced by factors such as infection, anesthesia, or drug use. Clinical manifestations of kernicterus are hypotonia, deafness, oculomotor palsy, lethargy, and, ultimately, death.

Causes

Both type 1 CNS and type 2 CNS are transmitted by autosomal recessive inheritance. Alterations in the coding sequence of the UGT1 gene result in absent or reduced UGT activity, with marked impairment of bilirubin conjugation. The UGT1 gene is located on 2q37. Several isoforms of UGT1 enzyme exist based on the variability in the amino-terminal region of the final protein. These differences are the result of alternative splicing among 10 different types of exon 1 at the 5' end of the UGT1 gene and constant exons 2-5 at the 3' end. Thus, the different UGT1 isoforms are distinguished according to the type of exon 1 they contain.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Hemolytic disorders
Neonatal jaundice
Breast milk jaundice

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Unconjugated hyperbilirubinemia in the presence of normal liver function test findings is characteristic of CNS. The usual bilirubin level is 17-50 mg/dL in type 1 CNS and 6-22 mg/dL in type 2. Higher bilirubin levels may be seen in type 2 CNS if coexisting hemolysis or intercurrent illness is present.
• Transferase activity measurements and the response to phenobarbital treatment distinguish type 1 CNS from type 2. Phenobarbital has no effect in type 1 CNS but causes an approximately 25% reduction in plasma bilirubin level in most patients with type 2 CNS.

Imaging Studies

• Findings on abdominal imaging studies, such as plain x-rays, CT scan, or ultrasound, are normal in CNS.

Histologic Findings

Liver histology findings are normal in CNS.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

Patients with type 2 CNS may not require any treatment or can be managed with phenobarbital. By contrast, prompt treatment of kernicterus is required in patients with type 1 CNS to avoid the potentially devastating neurological sequelae.

• Emergent management of bilirubin encephalopathy involves plasma exchange transfusion, which acts by removing the bilirubin-saturated albumin and provides free protein, which draws bilirubin from the tissues.
• Plasma exchange should be accompanied by long-term phototherapy, which helps in the conversion of bilirubin to more soluble isoforms that can be excreted in the urine. Oral calcium phosphate may be a useful adjuvant to phototherapy in type 1 CNS.
• Therapies based on gene and cell transfer techniques, although largely experimental at the present time, are likely to play an important role in the management of CNS in the future.
• Inhibitors of heme oxygenase, such as tin protoporphyrin or tin-mesoporphyrin, may be helpful in reducing bilirubin levels emergently, but the effect is short-lived.

Surgical Care

Liver transplantation has been attempted in select patients with type 1 CNS and has achieved good success rates.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Drug Category: Barbiturates

Used to avoid potentially devastating neurological sequelae in type 1 CNS and for the management of neurological symptoms in type 2 CNS.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Complications

• Prompt treatment of kernicterus in patients with type 1 CNS is required to prevent development of potentially devastating neurological sequelae.

Prognosis

• Untreated type 1 CNS is uniformly lethal by age 2 years, secondary to the development of kernicterus.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to make the diagnosis
• Failure to promptly and properly treat the condition
• Failure to consider concomitant illnesses

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

• Arias IM, Gartner LM, Cohen M. Chronic nonhemolytic unconjugated hyperbilirubinemia with glucuronyl transferase deficiency. Clinical, biochemical, pharmacologic and genetic evidence for heterogeneity. Am J Med. Sep 1969;47(3):395-409. [Medline].
• Costa E. Hematologically important mutations: bilirubin UDP-glucuronosyltransferase gene mutations in Gilbert and Crigler-Najjar syndromes. Blood Cells Mol Dis. Jan-Feb 2006;36(1):77-80.
• Gupta R, Parashar Y. Crigler-najjar syndrome type II. Indian J Pediatr. Nov 2004;71(11):1043.
• Jansen PL. Genetic diseases of bilirubin metabolism: the inherited unconjugated hyperbilirubinemias. J Hepatol. Sep 1996;25(3):398-404. [Medline].
• Jansen PL. Diagnosis and management of Crigler-Najjar syndrome. Eur J Pediatr. Dec 1999;158 Suppl 2:S89-94. [Medline].
• Lucey JF, Suresh GK, Kappas A. Crigler-Najjar syndrome, 1952-2000: learning from parents and patients about a very rare disease and using the internet to recruit patients for studies. Pediatrics. May 2000;105(5):1152-3. [Medline].
• Nowicki MJ, Poley JR. The hereditary hyperbilirubinaemias. Baillieres Clin Gastroenterol. Jun 1998;12(2):355-67. [Medline].
• Owens IS, Basu NK, Banerjee R. UDP-glucuronosyltransferases: gene structures of UGT1 and UGT2 families. Methods Enzymol. 2005;400:1-22.
• Petit FM, Gajdos V, Francoual J. Allelic heterogeneity of Crigler-Najjar type I syndrome: a study of 24 cases. Clin Genet. Dec 2004;66(6):571-2.
• Sampietro M, Iolascon A. Molecular pathology of Crigler-Najjar type I and II and Gilbert''s syndromes. Haematologica. Feb 1999;84(2):150-7.
• Servedio V, d''Apolito M, Maiorano N. Spectrum of UGT1A1 mutations in Crigler-Najjar (CN) syndrome patients: identification of twelve novel alleles and genotype-phenotype correlation. Hum Mutat. Mar 2005;25(3):325.
• Shevell MI, Majnemer A, Schiff D. Neurologic perspectives of Crigler-Najjar syndrome type I. J Child Neurol. Jun 1998;13(6):265-9.
• Sleisenger MH, Fordtran JS. Gastrointestinal Disease. Philadelphia, Pa:. WB Sanders Company;1993:Chapter 85.
• Takeuchi K, Kobayashi Y, Tamaki S. Genetic polymorphisms of bilirubin uridine diphosphate-glucuronosyltransferase gene in Japanese patients with Crigler-Najjar syndrome or Gilbert''s syndrome as well as in healthy Japanese subjects. J Gastroenterol Hepatol. Sep 2004;19(9):1023-8.

Article Last Updated: Aug 8, 2006