Crigler-Najjar syndrome - Revision history

Danbot: Strip excess bold

2026-03-22T09:29:47Z

Strip excess bold

Danbot: Moved intro paragraph into Background as bullets; removed excessive bold from bullet lead-ins; bold retained for critical items only

2026-03-19T14:13:31Z

Moved intro paragraph into Background as bullets; removed excessive bold from bullet lead-ins; bold retained for critical items only

Show changes

Ostermayer: Created page with "Crigler-Najjar syndrome (CNS) is a rare autosomal recessive disorder of bilirubin metabolism caused by '''absent (type 1) or severely reduced (type 2) UGT1A1 enzyme activity''', resulting in '''severe unconjugated hyperbilirubinemia''' from birth.Crigler-Najjar Syndrome. ''StatPearls''. NCBI. 2024. Type 1 is a '''life-threatening neonatal emergency''' — without aggressive phototherapy and ultimately liver transplantation, the accumulation o..."

2026-03-18T00:57:12Z

Created page with "Crigler-Najjar syndrome (CNS) is a rare autosomal recessive disorder of bilirubin metabolism caused by '''absent (type 1) or severely reduced (type 2) UGT1A1 enzyme activity''', resulting in '''severe unconjugated hyperbilirubinemia''' from birth.<ref name="StatPearls">Crigler-Najjar Syndrome. ''StatPearls''. NCBI. 2024.</ref> Type 1 is a '''life-threatening neonatal emergency''' — without aggressive phototherapy and ultimately liver transplantation, the accumulation o..."

New page

Crigler-Najjar syndrome (CNS) is a rare autosomal recessive disorder of bilirubin metabolism caused by '''absent (type 1) or severely reduced (type 2) UGT1A1 enzyme activity''', resulting in '''severe unconjugated hyperbilirubinemia''' from birth.<ref name="StatPearls">Crigler-Najjar Syndrome. ''StatPearls''. NCBI. 2024.</ref> Type 1 is a '''life-threatening neonatal emergency''' — without aggressive phototherapy and ultimately liver transplantation, the accumulation of unconjugated bilirubin causes '''kernicterus''' (irreversible bilirubin-induced brain damage).<ref name="MgmtCNS">Management of Crigler-Najjar syndrome. ''Expert Opin Orphan Drugs''. 2021. PMC8411811.</ref> Type 2 (Arias syndrome) is milder and manageable with phenobarbital. The emergency physician may encounter CNS as '''persistent severe neonatal jaundice unresponsive to standard phototherapy''', or as an '''acute bilirubin crisis''' in a known CNS patient triggered by illness, fasting, or surgery.

==Background==
*Extremely rare: estimated ~100 known type 1 cases worldwide at any given time; type 2 is somewhat more common<ref name="StatPearls"/>
*Higher prevalence in the Amish and Mennonite communities (founder effect)
*Exists on a spectrum with [[Gilbert syndrome]] — all three conditions involve UGT1A1 mutations but differ in severity:

{| class="wikitable"
|-
! Feature !! '''CN type 1''' !! '''CN type 2 (Arias)''' !! '''[[Gilbert syndrome]]'''
|-
| UGT1A1 activity || '''Absent''' || '''Markedly reduced''' (<10% of normal) || Reduced (~30% of normal)
|-
| Bilirubin level || '''20-50 mg/dL''' (can exceed 50) || '''6-20 mg/dL''' || Typically <3 mg/dL (rarely to 6)
|-
| Kernicterus risk || '''Very high''' — constant threat || Rare but possible (illness, anesthesia) || None
|-
| Response to phenobarbital || '''None''' (critical diagnostic distinction) || '''Yes''' (reduces bilirubin ~25%) || Yes (but not needed)
|-
| Treatment || '''Phototherapy 10-16 hours/day + liver transplant''' || Phenobarbital ± phototherapy || None required
|-
| Prognosis || Fatal without transplant; brain damage risk || Survival into adulthood; near-normal life || Normal lifespan; benign
|}

===Mechanism===
*UGT1A1 enzyme conjugates bilirubin with glucuronic acid → water-soluble conjugated bilirubin → excreted in bile
*In CN type 1: '''complete absence''' of UGT1A1 activity → no conjugation → unconjugated bilirubin accumulates to dangerous levels
*In CN type 2: '''severe reduction''' (<10%) of UGT1A1 activity → some conjugation occurs → lower bilirubin levels
*Unconjugated bilirubin is lipophilic and crosses the '''blood-brain barrier''' → deposits in basal ganglia, brainstem nuclei, cerebellum → '''kernicterus'''<ref name="StatPearls"/>

==Clinical features==
===CN type 1 — the neonatal emergency===
*'''Severe jaundice within the first days of life''' — total bilirubin typically 20-50 mg/dL; entirely unconjugated
*All other liver function tests '''completely normal''' (AST, ALT, alkaline phosphatase, albumin, coagulation studies)
*'''No evidence of hemolysis''' (normal reticulocyte count, haptoglobin, LDH, smear)
*Jaundice is '''persistent and progressive''' despite standard neonatal phototherapy
*'''Does NOT respond to phenobarbital''' — this distinguishes CN1 from CN2 and is a critical diagnostic feature<ref name="MgmtCNS"/>
*Without treatment, '''kernicterus develops''' — often within the first weeks to months of life

===Acute bilirubin encephalopathy (early kernicterus) — ED emergency signs===
*'''Lethargy, poor feeding, hypotonia''' (early)
*'''High-pitched cry'''
*'''Fever'''
*'''Irritability''' progressing to '''opisthotonus''' (arching of the back/neck — hypertonia)
*'''Seizures'''
*'''Apnea/respiratory failure'''
*'''Coma'''
*This is a '''medical emergency''' — bilirubin-induced brain damage may become irreversible within hours

===Chronic bilirubin encephalopathy (established kernicterus)===
*Choreoathetoid cerebral palsy (extrapyramidal movement disorder)
*Upward gaze palsy
*Sensorineural hearing loss (auditory neuropathy)
*Dental enamel hypoplasia
*Cognitive function often relatively preserved

===CN type 2 (Arias syndrome) — milder presentation===
*Intermittent mild-to-moderate jaundice (bilirubin 6-20 mg/dL)
*Typically diagnosed later in childhood or adolescence
*Jaundice worsens with '''illness, fasting, stress, surgery, anesthesia'''
*'''Responds to phenobarbital''' (bilirubin decreases ~25% within 2-3 weeks)
*Kernicterus is '''rare''' but has been reported, especially during intercurrent illness or general anesthesia<ref name="StatPearls"/>
*Most patients survive into adulthood without neurologic damage

===Known CNS patient presenting to the ED===
*'''Bilirubin crisis''' precipitated by:
**Intercurrent illness (infection, febrile illness)
**Fasting/dehydration
**Surgery/general anesthesia (bilirubin may rise dramatically perioperatively)
**Noncompliance with phototherapy (CN1)
**Discontinuation of phenobarbital (CN2)
*May present with worsening jaundice, signs of early encephalopathy, or family concern about rising bilirubin levels

==Differential diagnosis==
===Severe neonatal unconjugated hyperbilirubinemia===
*'''Crigler-Najjar syndrome type 1''' (bilirubin >20 mg/dL; no hemolysis; phenobarbital unresponsive)
*'''Crigler-Najjar syndrome type 2''' (bilirubin 6-20 mg/dL; phenobarbital responsive)
*'''Hemolytic disease of the newborn''' (Rh/ABO incompatibility, G6PD deficiency, hereditary spherocytosis) — positive Coombs test, elevated reticulocytes, abnormal smear
*'''Physiologic/breastfeeding jaundice''' — resolves; bilirubin typically <15 mg/dL
*'''[[Gilbert syndrome]]''' — bilirubin typically <6 mg/dL; does not cause kernicterus alone
*'''Sepsis''' — other systemic signs present
*'''Hypothyroidism''' — prolonged jaundice; check TSH

===Key distinguishing feature of CN type 1===
*'''Bilirubin >20 mg/dL that is entirely unconjugated''' + '''normal liver function''' + '''no hemolysis''' + '''no response to phenobarbital''' = CN type 1 until proven otherwise

==Evaluation==
===ED workup===
*'''Fractionated bilirubin''' (total and direct): confirms '''purely unconjugated''' hyperbilirubinemia
*'''Hepatic panel:''' AST, ALT, alkaline phosphatase, GGT, albumin — must be '''entirely normal''' (liver is structurally and functionally intact in CNS)
*'''Coagulation studies:''' PT/INR — normal (unless neonate has other vitamin K-related issues)
*'''CBC with reticulocyte count and peripheral smear:''' to exclude hemolysis
*'''Haptoglobin, LDH:''' normal (no hemolysis)
*'''Direct Coombs test:''' negative (excludes immune-mediated hemolysis)
*'''Blood type (mother and infant):''' to evaluate for ABO/Rh incompatibility
*'''TSH:''' to exclude hypothyroidism
*'''Blood glucose:''' neonates with severe jaundice may have concurrent hypoglycemia

===Confirmatory testing (arrange via specialist)===
*'''Phenobarbital trial:''' the most practical bedside distinguishing test between CN1 and CN2; phenobarbital (3-5 mg/kg/day for 2-3 weeks) will reduce bilirubin in CN2 but '''not in CN1'''<ref name="MgmtCNS"/>
*'''UGT1A1 gene sequencing:''' confirms diagnosis and distinguishes type 1 from type 2
*'''Bile analysis:''' near-complete absence of bilirubin conjugates in bile confirms CN1 (available via duodenal aspiration; not an ED test)

==Management==
===Acute bilirubin crisis (CN1 patient or any patient with bilirubin approaching kernicterus threshold)===
*'''Intensive phototherapy:''' initiate immediately<ref name="MgmtCNS"/>
**Blue LED light (wavelength 460-490 nm)
**Maximize body surface area exposure (undress the infant; use overhead and underneath light sources)
**Phototherapy converts unconjugated bilirubin into water-soluble photoisomers that can be excreted without conjugation
*'''Exchange transfusion:''' if bilirubin is at or above the exchange transfusion threshold for age, or if signs of acute bilirubin encephalopathy are present
**Rapidly removes circulating unconjugated bilirubin
**Double-volume exchange (twice the infant's blood volume)
*'''Plasmapheresis:''' alternative to exchange transfusion in older children/adults; effectively removes unconjugated bilirubin<ref name="NEJM_CNS">Fox IJ, et al. Treatment of the Crigler-Najjar Syndrome Type I with Hepatocyte Transplantation. ''N Engl J Med''. 1998;338(20):1422-1426.</ref>
*'''IV albumin:''' binds free unconjugated bilirubin in the blood and may reduce the fraction crossing the blood-brain barrier; give 1 g/kg IV before exchange transfusion
*'''Aggressive IV fluid hydration''' with dextrose-containing fluids
*'''Treat precipitating illness:''' antibiotics if infection; correct dehydration; resume nutrition
*'''Avoid drugs that displace bilirubin from albumin:''' sulfonamides, ceftriaxone, salicylates — these increase free (unbound) unconjugated bilirubin and worsen kernicterus risk

===Ongoing management of CN type 1===
*'''Daily phototherapy:''' 10-16 hours per day, lifelong (until liver transplant)<ref name="MgmtCNS"/>
**Phototherapy becomes '''less effective''' with age as skin thickens and body surface area-to-volume ratio decreases — this creates increasing risk of kernicterus around puberty
*'''Liver transplantation:''' the '''only definitive cure''' for CN type 1<ref name="StatPearls"/>
**Transplanted liver has normal UGT1A1 activity → bilirubin normalizes
**Post-transplant survival: 86-100% at 1 year, 79-92% at 10 years
**'''Prophylactic transplant is recommended before kernicterus develops''', as kernicterus may not be reversible
**Timing is difficult because onset of neurologic damage is unpredictable
*'''Hepatocyte transplantation:''' experimental; temporary reduction (~50%) in bilirubin; may bridge to transplant
*'''Gene therapy:''' AAV-mediated UGT1A1 gene delivery is in clinical trials; promising but not yet standard of care
*'''Adjunctive medications:''' calcium phosphate (bilirubin binder in gut), orlistat (reduces enterohepatic circulation), vitamin E, CoQ10, L-carnitine

===Management of CN type 2===
*'''Phenobarbital:''' 3-5 mg/kg/day; reduces bilirubin by ~25% through UGT1A1 enzyme induction; this is the mainstay of therapy<ref name="StatPearls"/>
*Phototherapy during acute exacerbations
*Liver transplantation '''rarely needed'''
*'''Avoid triggers:''' fasting, dehydration, intercurrent illness
*'''Perioperative planning:''' inform anesthesia and surgery teams; bilirubin may rise dramatically with general anesthesia; optimize phenobarbital, ensure phototherapy availability, consider perioperative albumin infusion

==Disposition==
*'''Neonate with suspected CN type 1 (severe unconjugated hyperbilirubinemia unresponsive to standard phototherapy):'''
**NICU admission
**Continuous intensive phototherapy
**Exchange transfusion if at threshold or encephalopathy present
**Genetics/metabolic and hepatology consultation
**Early referral to liver transplant center
*'''Known CN1 patient with bilirubin crisis:'''
**Admit (ICU if encephalopathy signs present)
**Intensive phototherapy; exchange transfusion/plasmapheresis if bilirubin critically elevated
**Identify and treat trigger
**Contact the patient's hepatologist/metabolic specialist
*'''Known CN2 patient with jaundice exacerbation:'''
**Ensure phenobarbital is being taken and at therapeutic levels
**Treat precipitating illness
**Phototherapy if bilirubin significantly elevated
**May be managed as outpatient if bilirubin is well below encephalopathy threshold and patient is clinically well; close follow-up
*'''General precautions for all CNS patients:'''
**Carry a '''medical alert identification'''
**Inform all healthcare providers of the diagnosis
**'''Avoid medications that displace bilirubin from albumin''' (sulfonamides, ceftriaxone, salicylates)
**'''Avoid prolonged fasting'''
**'''Surgical/anesthetic procedures require advance planning''' with the metabolic team

==See Also==
*[[Gilbert syndrome]]
*[[Neonatal jaundice]]
*[[Neonatal hepatitis]]
*[[Kernicterus]]
*[[Hemolytic disease of the newborn]]
*[[G6PD deficiency]]

==External Links==
*[https://www.ncbi.nlm.nih.gov/books/NBK562171/ StatPearls — Crigler-Najjar Syndrome]
*[https://pmc.ncbi.nlm.nih.gov/articles/PMC8411811/ Expert Opin Orphan Drugs — Management of Crigler-Najjar syndrome (2021)]
*[https://liverfoundation.org/liver-diseases/pediatric-liver-information-center/pediatric-liver-disease/crigler-najjar-syndrome/ American Liver Foundation — Crigler-Najjar Syndrome]
*[https://www.mdpi.com/1422-0067/25/20/11006 Int J Mol Sci — Therapeutic Options for Crigler-Najjar Syndrome: A Scoping Review (2024)]
*[https://pmc.ncbi.nlm.nih.gov/articles/PMC10433782/ Cureus — Liver Transplantation in a Child With Crigler-Najjar Syndrome Type I (2023)]

==References==
<references/>

[[Category:Pediatrics]]
[[Category:GI]]

← Older revision		Revision as of 09:29, 22 March 2026
Line 25:		Line 25:
	===Mechanism===		===Mechanism===
	*UGT1A1 enzyme conjugates bilirubin with glucuronic acid → water-soluble conjugated bilirubin → excreted in bile		*UGT1A1 enzyme conjugates bilirubin with glucuronic acid → water-soluble conjugated bilirubin → excreted in bile
	*In CN type 1: ~~'''~~complete absence~~'''~~ of UGT1A1 activity → no conjugation → unconjugated bilirubin accumulates to dangerous levels		*In CN type 1: complete absence of UGT1A1 activity → no conjugation → unconjugated bilirubin accumulates to dangerous levels
	*In CN type 2: ~~'''~~severe reduction~~'''~~ (<10%) of UGT1A1 activity → some conjugation occurs → lower bilirubin levels		*In CN type 2: severe reduction (<10%) of UGT1A1 activity → some conjugation occurs → lower bilirubin levels
	*Unconjugated bilirubin is lipophilic and crosses the '''blood-brain barrier''' → deposits in basal ganglia, brainstem nuclei, cerebellum → '''kernicterus'''<ref name="StatPearls"/>		*Unconjugated bilirubin is lipophilic and crosses the '''blood-brain barrier''' → deposits in basal ganglia, brainstem nuclei, cerebellum → '''kernicterus'''<ref name="StatPearls"/>

Line 32:		Line 32:
	===CN type 1 — the neonatal emergency===		===CN type 1 — the neonatal emergency===
	* Severe jaundice within the first days of life — total bilirubin typically 20-50 mg/dL; entirely unconjugated		* Severe jaundice within the first days of life — total bilirubin typically 20-50 mg/dL; entirely unconjugated
	*All other liver function tests ~~'''~~completely normal~~'''~~ (AST, ALT, alkaline phosphatase, albumin, coagulation studies)		*All other liver function tests completely normal (AST, ALT, alkaline phosphatase, albumin, coagulation studies)
	* No evidence of hemolysis (normal reticulocyte count, haptoglobin, LDH, smear)		* No evidence of hemolysis (normal reticulocyte count, haptoglobin, LDH, smear)
	*Jaundice is ~~'''~~persistent and progressive~~'''~~ despite standard neonatal phototherapy		*Jaundice is persistent and progressive despite standard neonatal phototherapy
	* Does NOT respond to phenobarbital — this distinguishes CN1 from CN2 and is a critical diagnostic feature<ref name="MgmtCNS"/>		* Does NOT respond to phenobarbital — this distinguishes CN1 from CN2 and is a critical diagnostic feature<ref name="MgmtCNS"/>
	*Without treatment, ~~'''~~kernicterus develops~~'''~~ — often within the first weeks to months of life		*Without treatment, kernicterus develops — often within the first weeks to months of life

	===Acute bilirubin encephalopathy (early kernicterus) — ED emergency signs===		===Acute bilirubin encephalopathy (early kernicterus) — ED emergency signs===
Line 42:		Line 42:
	* High-pitched cry		* High-pitched cry
	* Fever		* Fever
	* Irritability progressing to ~~'''~~opisthotonus~~'''~~ (arching of the back/neck — hypertonia)		* Irritability progressing to opisthotonus (arching of the back/neck — hypertonia)
	* Seizures		* Seizures
	* Apnea/respiratory failure		* Apnea/respiratory failure
Line 58:		Line 58:
	*Intermittent mild-to-moderate jaundice (bilirubin 6-20 mg/dL)		*Intermittent mild-to-moderate jaundice (bilirubin 6-20 mg/dL)
	*Typically diagnosed later in childhood or adolescence		*Typically diagnosed later in childhood or adolescence
	*Jaundice worsens with ~~'''~~illness, fasting, stress, surgery, anesthesia~~'''~~		*Jaundice worsens with illness, fasting, stress, surgery, anesthesia
	* Responds to phenobarbital (bilirubin decreases ~25% within 2-3 weeks)		* Responds to phenobarbital (bilirubin decreases ~25% within 2-3 weeks)
	*Kernicterus is '''rare''' but has been reported, especially during intercurrent illness or general anesthesia<ref name="StatPearls"/>		*Kernicterus is '''rare''' but has been reported, especially during intercurrent illness or general anesthesia<ref name="StatPearls"/>
Line 83:		Line 83:

	===Key distinguishing feature of CN type 1===		===Key distinguishing feature of CN type 1===
	* Bilirubin >20 mg/dL that is entirely unconjugated + ~~'''~~normal liver function~~'''~~ + ~~'''~~no hemolysis~~'''~~ + ~~'''~~no response to phenobarbital~~'''~~ = CN type 1 until proven otherwise		* Bilirubin >20 mg/dL that is entirely unconjugated + normal liver function + no hemolysis + no response to phenobarbital = CN type 1 until proven otherwise

	==Evaluation==		==Evaluation==
	===ED workup===		===ED workup===
	* Fractionated bilirubin (total and direct): confirms ~~'''~~purely unconjugated~~'''~~ hyperbilirubinemia		* Fractionated bilirubin (total and direct): confirms purely unconjugated hyperbilirubinemia
	* Hepatic panel: AST, ALT, alkaline phosphatase, GGT, albumin — must be '''entirely normal''' (liver is structurally and functionally intact in CNS)		* Hepatic panel: AST, ALT, alkaline phosphatase, GGT, albumin — must be '''entirely normal''' (liver is structurally and functionally intact in CNS)
	* Coagulation studies: PT/INR — normal (unless neonate has other vitamin K-related issues)		* Coagulation studies: PT/INR — normal (unless neonate has other vitamin K-related issues)
Line 98:		Line 98:

	===Confirmatory testing (arrange via specialist)===		===Confirmatory testing (arrange via specialist)===
	* Phenobarbital trial: the most practical bedside distinguishing test between CN1 and CN2; phenobarbital (3-5 mg/kg/day for 2-3 weeks) will reduce bilirubin in CN2 but ~~'''~~not in CN1~~'''~~<ref name="MgmtCNS"/>		* Phenobarbital trial: the most practical bedside distinguishing test between CN1 and CN2; phenobarbital (3-5 mg/kg/day for 2-3 weeks) will reduce bilirubin in CN2 but not in CN1<ref name="MgmtCNS"/>
	* UGT1A1 gene sequencing: confirms diagnosis and distinguishes type 1 from type 2		* UGT1A1 gene sequencing: confirms diagnosis and distinguishes type 1 from type 2
	* Bile analysis: near-complete absence of bilirubin conjugates in bile confirms CN1 (available via duodenal aspiration; not an ED test)		* Bile analysis: near-complete absence of bilirubin conjugates in bile confirms CN1 (available via duodenal aspiration; not an ED test)
Line 119:		Line 119:
	===Ongoing management of CN type 1===		===Ongoing management of CN type 1===
	* Daily phototherapy: 10-16 hours per day, lifelong (until liver transplant)<ref name="MgmtCNS"/>		* Daily phototherapy: 10-16 hours per day, lifelong (until liver transplant)<ref name="MgmtCNS"/>
	**Phototherapy becomes ~~'''~~less effective~~'''~~ with age as skin thickens and body surface area-to-volume ratio decreases — this creates increasing risk of kernicterus around puberty		**Phototherapy becomes less effective with age as skin thickens and body surface area-to-volume ratio decreases — this creates increasing risk of kernicterus around puberty
	* Liver transplantation: the '''only definitive cure''' for CN type 1<ref name="StatPearls"/>		* Liver transplantation: the '''only definitive cure''' for CN type 1<ref name="StatPearls"/>
	**Transplanted liver has normal UGT1A1 activity → bilirubin normalizes		**Transplanted liver has normal UGT1A1 activity → bilirubin normalizes
Line 132:		Line 132:
	* Phenobarbital: 3-5 mg/kg/day; reduces bilirubin by ~25% through UGT1A1 enzyme induction; this is the mainstay of therapy<ref name="StatPearls"/>		* Phenobarbital: 3-5 mg/kg/day; reduces bilirubin by ~25% through UGT1A1 enzyme induction; this is the mainstay of therapy<ref name="StatPearls"/>
	*Phototherapy during acute exacerbations		*Phototherapy during acute exacerbations
	*Liver transplantation ~~'''~~rarely needed~~'''~~		*Liver transplantation rarely needed
	* Avoid triggers: fasting, dehydration, intercurrent illness		* Avoid triggers: fasting, dehydration, intercurrent illness
	* Perioperative planning: inform anesthesia and surgery teams; bilirubin may rise dramatically with general anesthesia; optimize phenobarbital, ensure phototherapy availability, consider perioperative albumin infusion		* Perioperative planning: inform anesthesia and surgery teams; bilirubin may rise dramatically with general anesthesia; optimize phenobarbital, ensure phototherapy availability, consider perioperative albumin infusion
Line 154:		Line 154:
	**May be managed as outpatient if bilirubin is well below encephalopathy threshold and patient is clinically well; close follow-up		**May be managed as outpatient if bilirubin is well below encephalopathy threshold and patient is clinically well; close follow-up
	* General precautions for all CNS patients:		* General precautions for all CNS patients:
	**Carry a ~~'''~~medical alert identification~~'''~~		**Carry a medical alert identification
	**Inform all healthcare providers of the diagnosis		**Inform all healthcare providers of the diagnosis
	** Avoid medications that displace bilirubin from albumin (sulfonamides, ceftriaxone, salicylates)		** Avoid medications that displace bilirubin from albumin (sulfonamides, ceftriaxone, salicylates)