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ORPHA:79235

Crigler-Najjar syndrome type 2

low confidenceSubtype of disorder

Also known as: Bilirubin uridinediphosphate glucuronosyltransferase deficiency type 2 · Bilirubin-UGT deficiency type 2

Publications

11,470

Trials

0

Interventional, condition-specific

Researchers

332

Distinct authors in sample

Gene link

UGT1A1

Definitive

Readiness

4/6

Stages with a signal

Clinical definition (Orphanet)

A form of Crigler Najjar syndrome (CNS), a rare disorder of bilirubin metabolism, characterized by unconjugated hyperbilirubinemia due to reduced and inducible activity of hepatic UDP-glucuronosyltransferase 1A1. The disorder clinically manifests with , isolated jaundice with a risk of developing bilirubin later in life due to triggers such as stress or infection.

How rare: How common this is has not been clearly measured.

Orphanet entry

Cross-references

Joined from Mondo / Orphanet. MeSH labels may enter searches; UMLS / OMIM / NCIT are stored for reference.

Additional Mondo synonyms (5)

Arias syndrome · UGT deficiency type 2 · bilirubin uridinediphosphate glucuronosyltransferase deficiency type 2 · bilirubin-UGT deficiency type 2 · hereditary unconjugated hyperbilirubinemia type 2

Research stages

Trial readiness signals

Where this condition sits on an open-data research pipeline — not how close a treatment is, and not medical advice. Empty stages often mean “not in these databases under this Mondo ID,” not “impossible.”

4/6 stages with a signal

No specific-condition interventional trial, but broader-category trials exist — discuss eligibility with a clinician.

  1. Gene identifiedPresent

    Definitive — UGT1A1

  2. LiteraturePresent

    11,470 matched papers (6,775 in last 10 years) Source

  3. Phenotype characterisedPresent

    7 HPO annotations (e.g. Unconjugated hyperbilirubinemia; Elevated circulating hepatic transaminase concentration; Reduced tissue UDP-glucuronyl-transferase activity) Source

  4. Animal modelNot found

    No Alliance genotype “model of” associations via Monarch for these Mondo IDs

  5. Orphan designationNot found

    No FDA or EMA orphan-drug designation matched this disease via UMLS or preferred name Source

  6. Interventional trialPartial

    None under the specific name; 7 for broader category Crigler-Najjar syndrome

Biology

Genes and phenotypes

Gene–disease validity from GenCC, plus phenotypes and animal models joined from Monarch Initiative via Mondo ID — not a clinical diagnosis aid.

Do we know what causes it?

Yes — we know a specific gene responsible (UGT1A1).

GenCC classification: Definitive.

Phenotypes (Monarch / HPO)

7

Associated phenotypes · MONDO:0011725

  • Unconjugated hyperbilirubinemia
  • Elevated circulating hepatic transaminase concentration
  • Reduced tissue UDP-glucuronyl-transferase activity
  • Jaundice
  • Prolonged neonatal jaundice

Showing 5 of 7 — open Monarch for the full list.

Animal models (Monarch / Alliance)

None returned for this Mondo ID. Empty here is not proof that no model organism work exists under another name or gene.

Monarch fetch 2026-07-29

Therapies

Designations, candidates, and chemicals

FDA OOPD and EMA orphan designations, Open Targets clinical candidates, and CTD chemical associations via MyDisease.info. These never change the interventional-trial headline.

Orphan designation (FDA · EMA)

No designation matched this disease via UMLS or preferred name on the FDA OOPD mirror or EMA orphan register. Absence here is not proof that none exists under another wording.

Open Targets candidates

No drugs or clinical candidates returned for this Mondo ID on Open Targets.

CTD chemicals (MyDisease.info)

No CTD chemical associations returned for this Mondo ID.

Literature

Is anyone studying this?

11,470

11,470 papers — among the better-studied rare conditions, though still a fraction of common-disease literature (breast cancer: over 700,000). Median papers in the last 10 years for a rare disease in this dataset (publications denominator n=3967) is 59.

11,470 papers since the earliest indexed year in this search — median last-10-year count for a rare disease in this dataset is 59 (publications denominator n=3967).

6,775 in the last 10 years · low confidence

Phrase hits: 63 · MeSH hits: 2

Open Europe PMC search

Who's working on it?

332

Distinct author names in 63 sampled papers — named people below.

Who's working on it?

No interventional trial matched this name; these authors publish on it in the sampled literature — a practical starting point for contact.

  1. 01
    Huang CS5 papers · 2024

    Department of Clinical Pathology, Cathay General Hospital, Taipei, Taiwan.

    Papers in Europe PMC
  2. 02
    Huang MJ4 papers · 2022

    Department of Laboratory Medicine, Cathay General Hospital, 280, Jen Ai-Road, Section 4, Taipei 106, Taiwan, China.

    Papers in Europe PMC
  3. 03
    Saxena R4 papers · 2017

    Department of Genetic Medicine, Sir Ganga Ram Hospital, New Delhi, India.

    Papers in Europe PMC
  4. 04
    Yang SS3 papers · 2019

    Liver Unit, Cathay General Hospital, Taipei, Taiwan.

    Papers in Europe PMC
  5. 05
    Adachi Y2 papers · 2006
    Papers in Europe PMC
  6. 06
    Araki J2 papers · 2006
    Papers in Europe PMC
  7. 07
    Burchell B2 papers · 2001
    Papers in Europe PMC
  8. 08
    Chen PL2 papers · 2022

    Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan.

    Papers in Europe PMC
  9. 09
    Chen X2 papers · 2025

    Department of Chest Surgery, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Linhai, China.

    Papers in Europe PMC
  10. 10
    Chen Y2 papers · 2025

    Department of Chest Surgery, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Linhai, China.

    Papers in Europe PMC

Clinical research

Is a treatment being tested?

0

interventional trials for this specific condition

No interventional trial testing a treatment matched this specific condition name on ClinicalTrials.gov (observational studies and pan-disease registries are listed separately when present). 7 trials are registered for Crigler-Najjar syndrome, the broader category — shown separately because they may or may not enrol this specific subtype.

Data as of 11 September 2026 · last trial check 11 September 2026

No matched interventional trials. This is true for 77.2% of diseases in the trials denominator (5501 of 7126). Here are the researchers publishing on it.

low confidence · 38.6th percentile (trials denominator)

Recruiting interventional trials

From the matched ClinicalTrials.gov set

No interventional trial testing a treatment was found for this specific condition name on ClinicalTrials.gov.

7 interventional trials matched Crigler-Najjar syndrome, the broader category — listed below. Those studies are not counted in the condition-specific total.

Broader category: Crigler-Najjar syndrome

7

Interventional trials for the parent category, exclusive of NCT IDs already counted above. Eligibility for this subtype is not guaranteed.

Worth raising with a clinician. How we count trials.

Recruiting under the broader category

Other registries (secondary)

Broader net from EU CTIS, ISRCTN, and ICTRP when available — deduped against ClinicalTrials.gov IDs already counted above. Dual-model LLM relevance gates what we keep. These rows are not added to the interventional headline.

raw 1 · after dedupe 1 · already on CT.gov 0 · kept 0 · parent 0 · uncertain 1 · dropped 0 · fetched 2026-07-30

Source notes: ictrp: Error: ICTRP public search unavailable (WHO portal is SPA-only; SOAP needs partnership). Tried: https://apps.who.int/tri

No secondary-registry studies passed dual-model relevance for this condition name (after dedupe).

Uncertain / not reviewed (1)

Where to find support

Condition-specific patient organisations, when Orphanet lists them, are on the disease’s Orphanet page. We also link umbrella groups that support undiagnosed and ultra-rare families.

Orphanet entry for Crigler-Najjar syndrome type 2 — check Associations / patient organisations on that page.

India — NPRD

Last verified 2026-07-26

This ORPHAcode is not on our curated NPRD list (direct or Mondo-parent match). That does not decide clinical eligibility; families in India should ask a notified Centre of Excellence about current coverage.

Hand-curated for this project. ORPHAcode mappings are best-effort and may be incomplete or imprecise for umbrella categories. Parent (Mondo) matches mean the policy lists a broader category — confirm eligibility with a Centre of Excellence. Financial entitlements summarised from public policy statements and may change. This is not official government guidance.

How we counted this

Europe PMC query (preferred label + any corrected label + Orphanet and Mondo exact synonyms, stoplisted; unioned with resolved MeSH labels when available). UMLS / OMIM / NCIT cross-references are stored on the overview but are not added to the query string.

("Crigler-Najjar syndrome type 2" OR "Bilirubin uridinediphosphate glucuronosyltransferase deficiency type 2" OR "Bilirubin-UGT deficiency type 2" OR "Arias syndrome" OR "UGT deficiency type 2" OR "hereditary unconjugated hyperbilirubinemia type 2") OR (MESH:"Crigler Najjar syndrome, type 2") OR ("UGT1A1" OR "UGT1A1 syndrome" OR "UGT1A1-related")

Run this search on Europe PMC

MeSH descriptor terms unioned into the query: Crigler Najjar syndrome, type 2

ClinicalTrials.gov query (quoted phrases + MeSH via query.cond, plus recall-expansion terms when used):

"Crigler-Najjar syndrome type 2" OR "Bilirubin uridinediphosphate glucuronosyltransferase deficiency type 2" OR "Bilirubin-UGT deficiency type 2" OR "Arias syndrome" OR "UGT deficiency type 2" OR "hereditary unconjugated hyperbilirubinemia type 2" OR "Crigler Najjar syndrome, type 2"

Study-type breakdown: 0 interventional · 0 observational · 0 expanded access. Only interventional studies enter the trial headline.

Parent-category trials query:

"Crigler-Najjar syndrome"

Query health: ok — strategies attempted: phrase, mesh; with hits: phrase, mesh

Run this search on ClinicalTrials.gov

Confidence reasoning

  • Preferred label is multi-word and distinctive
  • No synonyms dropped by stoplist
  • No label/synonym collisions with other diseases in this corpus
  • Publication count (11470) is extremely high with unknown/missing prevalence — treat as possible over-matching, not proven research intensity

Ingested 2026-07-27T02:06:29.121Z