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# Crigler-Najjar syndrome

A very rare inherited disease in which the liver barely conjugates bilirubin; in type 1 severe jaundice threatens the brain from birth.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Liver](https://durgical.com/en/anatomy/liver/)
- [Globus pallidus](https://durgical.com/en/anatomy/globus-pallidus/)
- [Caudate nucleus](https://durgical.com/en/anatomy/caudate-nucleus/)
- [Sclera](https://durgical.com/en/anatomy/sclera/)

## In biochemistry

- [Heme breakdown and bilirubin: Step 3 · UDP-glucuronosyltransferase 1A1 (UGT1A1)](https://durgical.com/en/biochemistry/pathways/heme-breakdown-and-bilirubin/#paso-3)
- [Uronic acid pathway](https://durgical.com/en/biochemistry/topics/uronic-acid-pathway/)
- [UGT1A1 (bilirubin UDP-glucuronosyltransferase)](https://durgical.com/en/biochemistry/enzymes/ugt1a1/)
- [Bilirubin](https://durgical.com/en/biochemistry/molecules/bilirubin/)
- [Glucuronidation](https://durgical.com/en/biochemistry/topics/glucuronidation/)

## Why it happens

- [Pigments in tissue: lipofuscin, hemosiderin, melanin, bilirubin, carbon](https://durgical.com/en/general-pathology/pigments-in-tissue-lipofuscin-hemosiderin-melanin-bilirubin-carbon/)

## What it is

Severe unconjugated hyperbilirubinemia from absent (type 1) or markedly reduced (type 2) liver UGT1A1.

## Who gets it

It affects fewer than 1 in a million newborns; it is more common where there is consanguinity.

## Causes

- Autosomal recessive inheritance: two UGT1A1 variants

## Risk factors

- Consanguineous parents
- An affected sibling

## Pathophysiology

Without conjugation, indirect bilirubin cannot leave through bile and builds up. The free, fat-soluble fraction crosses the blood–brain barrier and deposits in the basal ganglia, brainstem and [cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/) (kernicterus).

## Classification

- Type 1: no UGT1A1 activity; very high bilirubin; no response to phenobarbital
- Type 2 (Arias): activity under 10 %; lower bilirubin; responds to phenobarbital

## Symptoms and signs

- Intense jaundice from the first days of life
- Drowsiness, poor feeding and hypotonia in the newborn
- In type 2, milder jaundice that worsens with fasting or infection

## Red flags

- High-pitched cry, arching, fever or seizures (bilirubin encephalopathy)

## Diagnosis

**Clinical**
Severe, persistent unconjugated jaundice without hemolysis or [liver](https://durgical.com/en/anatomy/liver/) disease.

**Tests**
Very high indirect bilirubin (type 1 often above 20 mg/dL) with normal liver tests; no hemolysis; bilirubin response to phenobarbital (separates types 1 and 2); UGT1A1 gene testing.

**Imaging**
Brain MRI if kernicterus is suspected (signal in the [globus pallidus](https://durgical.com/en/anatomy/globus-pallidus/)).

## Treatment

**Procedure**
Intense daily phototherapy (type 1), several hours each day

**Acute**
Exchange transfusion or plasmapheresis in crises of very high bilirubin

**Medical**
Phenobarbital in type 2, which induces the remaining enzyme

**Surgical**
Liver transplantation, the definitive cure for type 1

## Complications

- Kernicterus: choreoathetoid cerebral palsy, deafness, limited upward gaze
- Pigment gallstones

## Prognosis

Type 2 has a good prognosis; type 1 depends on constant phototherapy and transplantation.

## Test yourself

Think of the answer, then tap the question to see it.

## How is Crigler-Najjar type 1 distinguished from type 2?

Type 2 keeps some UGT1A1 and bilirubin falls with phenobarbital; type 1 does not respond.

## What is the most feared complication of type 1?

Kernicterus: unconjugated bilirubin deposited in the basal ganglia.

## Which treatment cures type 1?

Liver transplantation, which supplies functional UGT1A1.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/conditions/crigler-najjar-syndrome/)

## Related conditions

- [Gilbert syndrome](https://durgical.com/en/conditions/gilbert-syndrome/)
- [Neonatal jaundice](https://durgical.com/en/conditions/neonatal-jaundice/)
- [Gallstones (cholelithiasis)](https://durgical.com/en/conditions/gallstones/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Crigler-Najjar syndrome: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/crigler-najjar-syndrome/) (MedlinePlus, US National Library of Medicine, 2026); [UGT1A1 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/ugt1a1/) (MedlinePlus, US National Library of Medicine, 2026); [Bilirubin blood test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003479.htm) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/conditions/crigler-najjar-syndrome/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/crigler-najjar-syndrome/