Crigler-Najjar Syndrome, Type Ii (CN2)

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OMIM 57 606785 PS237450 MESH via Orphanet 45 C536213 ICD10 via Orphanet 34 E80.5 UMLS via Orphanet 73 C0268311 C2931132

Orphanet 59 ORPHA79235 MedGen 42 C0268311 C2931132 UMLS 72 C2931132

NIH Rare Diseases : ⁵³ Crigler-Najjar syndrome type 2 (CN-2) is a rare disorder that causes elevated levels of bilirubin in the blood (hyperbilirubinemia). Bilirubin normally is made by the body when old red blood cells are broken down. However, people with CN-2 develop hyperbilirubinemia even when red blood cells are not excessively broken down, because they have too little of a liver enzyme needed for conversion and excretion of bilirubin. The main symptom of CN-2 is persistent jaundice, which is yellowing of the skin, mucous membranes and whites of the eyes. Jaundice may become noticeable in infancy (particularly when an infant is sick or has not eaten for an extended time), but some people with CN-2 are not diagnosed until adulthood. Rarely, a person with CN-2 may develop bilirubin encephalopathy (also called kernicterus), especially during illness, prolonged fasting, or while under anesthesia. CN-2 is caused by mutations in the UGT1A1 gene and inheritance is autosomal recessive. CN-2 responds to treatment with phenobarbital; however during an episode of severe hyperbilirubinemia, phototherapy may be needed. Not all people with CN-2 require treatment, but routine monitoring is still recommended. Of note, mutations in the UGT1A1 gene can alternatively cause other disorders, such as Crigler-Najjar syndrome type 1 (CN-1) and Gilbert syndrome. CN-1 is characterized by near or complete absence of enzyme activity (versus partial absence in type 2) and severe, life-threatening symptoms. Phenobarbitol treatment is ineffective for people with CN-1, which is treated differently. Gilbert syndrome is considered a mild liver disorder that often does not cause symptoms or causes mild jaundice. Sometimes it can be hard to distinguish between Gilbert syndrome and CN-2 because of considerable overlap in measured bilirubin levels. Genetic testing to identify the specific mutation present is sometimes needed for the correct diagnosis.

MalaCards based summary : Crigler-Najjar Syndrome, Type Ii, also known as crigler-najjar syndrome type 2, is related to crigler-najjar syndrome, type i and kernicterus, and has symptoms including icterus An important gene associated with Crigler-Najjar Syndrome, Type Ii is UGT1A1 (UDP Glucuronosyltransferase Family 1 Member A1), and among its related pathways/superpathways are Metabolism and Cytochrome P450 - arranged by substrate type. Affiliated tissues include liver, testes and skin, and related phenotypes are unconjugated hyperbilirubinemia and prolonged neonatal jaundice

OMIM : ⁵⁷ The hereditary hyperbilirubinemias (Wolkoff et al., 1983) include (1) those resulting in predominantly unconjugated hyperbilirubinemia: Gilbert or Arias syndrome, Crigler-Najjar syndrome type I, and Crigler-Najjar syndrome type II; and (2) those resulting in predominantly conjugated hyperbilirubinemia: Dubin-Johnson syndrome (237500), Rotor syndrome (237450), and several forms of intrahepatic cholestasis (147480, 211600, 214950, 243300). Detailed studies show that patients with Crigler-Najjar syndrome type II have reduced activity of bilirubin glucuronosyltransferase (Labrune et al., 1989, Seppen et al., 1994). (606785)

UniProtKB/Swiss-Prot : ⁷⁴ Crigler-Najjar syndrome 2: Patients have less severe hyperbilirubinemia and usually survive into adulthood without neurologic damage. Phenobarbital, which induces the partially deficient glucuronyl transferase, can diminish the jaundice. CN2 inheritance is autosomal dominant.

Clinical features from OMIM:

606785

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