Crigler-Najjar syndrome: genes and variants
Crigler-Najjar syndrome is linked to 1 analyzed protein (UGT1A1). 14 DNA variants are known to cause it; 38 more are uncertain, and 0 of those already look disease-causing on computable evidence.
Last updated 2026-09-30. Research information, not medical advice.
Also known as: Crigler-Najjar syndrome type 1; Crigler-Najjar syndrome type 2; Crigler-Najjar syndrome, type II
Genes linked to Crigler-Najjar syndrome
UGT1A1: UDP-glucuronosyltransferase 1A1
It conjugates bilirubin and many lipophilic compounds with glucuronic acid, enabling efficient elimination in bile or urine. Reduced activity causes Gilbert syndrome or Crigler-Najjar syndrome and can also increase toxicity from drugs such as irinotecan.
14 disease-causing and 38 uncertain variants in UGT1A1 are linked to Crigler-Najjar syndrome.
Known disease-causing variants in Crigler-Najjar syndrome
| Variant | Position | Protein part | Clinical label |
|---|---|---|---|
| UGT1A1 R336W | 336 | Disease-causing (★★) | |
| UGT1A1 R209W | 209 | Disease-causing (★★) | |
| UGT1A1 R336Q | 336 | Disease-causing (★★) | |
| UGT1A1 P387R | 387 | Disease-causing (★★) | |
| UGT1A1 Y486D | 486 | Disease-causing (★★) | |
| UGT1A1 Q331R | 331 | Disease-causing (★★) | |
| UGT1A1 Q357R | 357 | Disease-causing (★★) | |
| UGT1A1 S375F | 375 | Disease-causing (★★) | |
| UGT1A1 G276R | 276 | Disease-causing (★) | |
| UGT1A1 L443P | 443 | Disease-causing (★) | |
| UGT1A1 G395V | 395 | Disease-causing (★) | |
| UGT1A1 L15R | 15 | Disease-causing (★) | |
| UGT1A1 F83L | 83 | Disease-causing (★) | |
| UGT1A1 R450L | 450 | Disease-causing (★) |
Same protein, different disease
- Gilbert syndrome is also caused by UGT1A1 variants; they fall mostly in different places as the Crigler-Najjar syndrome variants (10 disease-causing).
Diseases related to Crigler-Najjar syndrome
- Gilbert syndrome, also linked to UGT1A1
- Lucey-Driscoll syndrome, also linked to UGT1A1
- BILIRUBIN, SERUM LEVEL OF, QUANTITATIVE TRAIT LOCUS 1, also linked to UGT1A1
Frequently asked questions
Which genes are linked to Crigler-Najjar syndrome?
In CATVariant, Crigler-Najjar syndrome is linked to 1 analyzed protein: UGT1A1 (UDP-glucuronosyltransferase 1A1).
How many genetic variants are linked to Crigler-Najjar syndrome?
83 variants: 14 are classified as disease-causing (pathogenic or likely pathogenic) in ClinVar and 38 are of uncertain significance or have conflicting reports.
Which uncertain variants in Crigler-Najjar syndrome look disease-causing?
None of the uncertain variants currently reaches the likely-pathogenic range on computable evidence alone.
About this data
Variant–disease links come from ClinVar, Open Targets and UniProt, pooled from the latest public CATVariant analysis of each human protein. Evidence scores use the ACMG/AMP Bayesian points scale with computable criteria only (position among known disease variants, rarity in gnomAD, calibrated predictors, deep mutational scanning); there is no family or patient data, so they prioritise variants for expert review and never classify them.
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