Crigler-Najjar Syndrome: Symptoms, Causes, and Treatment Options

Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026

Quick Answer

Crigler-Najjar syndrome is a rare inherited condition in which a UGT1A1 gene mutation stops the liver from processing toxic bilirubin, causing persistent jaundice and, if untreated, potentially fatal brain damage called kernicterus [1] [3]. Type 1 is severe and often life-threatening without a liver transplant; Type 2 is milder [1] [3]. Phototherapy is the most common ongoing treatment, and transplant is considered a cure [1].

What the research says

• In type 1, bilirubin can reach dangerous levels within days. A systematic review found that in complete UGT1A1 deficiency, unconjugated bilirubin rises 3 to 6 mg/dL per day in the newborn period and reaches neurologically dangerous levels between 5 and 14 days of age. Phototherapy is the mainstay of treatment but is demanding for families, and liver transplantation is the only definitive therapy, with excellent long-term survival increasingly reported (PubMed: Dhawan et al., J Gastroenterol Hepatol, 2019 [6]).

• Transplant timing matters, and newer options are being studied. A 2024 scoping review concluded that liver transplantation remains the only definitive cure for type 1 and must happen before irreversible brain damage. It also notes the downsides (graft rejection and lifelong immunosuppression) and describes gene therapy and autologous hepatocyte transplantation as promising alternatives still under study (PubMed: Sambati et al., Int J Mol Sci, 2024 [7]).

• Gene therapy has shown early results in a small trial. In a phase 1-2 study of 5 patients treated with phototherapy, a single infusion of an AAV8 vector carrying UGT1A1 caused no serious adverse events. The patients who received the higher dose had lower bilirubin and were off phototherapy at least 78 weeks later. This is an early, small study and not yet a standard treatment (PubMed: D'Antiga et al., N Engl J Med, 2023 [8]).

What Is Crigler-Najjar Syndrome?

Crigler-Najjar syndrome is a rare genetic condition in which the liver cannot break down bilirubin, a yellow substance that forms when red blood cells reach the end of their lifespan [1]. Your liver normally converts bilirubin from a toxic form into a nontoxic form that is eliminated from your body in stool [1]. When this process fails, toxic bilirubin collects in the blood and tissues instead [1].

The condition shows up as jaundice, a yellowing of the skin and the whites of the eyes, that lasts long after the typical newborn period [1]. Beyond the visible yellow tint, untreated bilirubin buildup can cause life-threatening symptoms and irreversible brain damage [1] [3].

Key fact	Detail
What it is	Rare genetic condition in which the liver cannot break down bilirubin [1]
Cause	Mutation in the UGT1A1 gene (autosomal recessive inheritance) [3] [4]
How common	Fewer than 1 in 1 million newborns worldwide [1] [3]
Main symptom	Persistent jaundice (yellow skin and eyes) beyond the newborn period [1]
Main danger	Bilirubin buildup in the brain (kernicterus), causing irreversible damage [1]
Types	Type 1 (severe, life-threatening) and Type 2 (milder, normal life expectancy) [1]
Cure	Liver transplant can effectively cure the condition [1]
Prevention	Not possible, because it is a genetic condition

Figure 1: Crigler-Najjar syndrome at a glance: the bilirubin breakdown failure, how rare it is, the main symptom, and the biggest risk.

How is Crigler-Najjar syndrome type 1 different from type 2?

Crigler-Najjar syndrome has two types: type 1 carries a poorer prognosis without early treatment, while type 2 has a good prognosis when treated early [1].

Feature	Type 1 (CN1)	Type 2 (CN2)
Severity	Very severe, life-threatening [1]	Less severe, mild symptoms [1]
Typical prognosis without treatment	Many children do not survive past childhood from complications [1]	Normal life expectancy [1]
Response to phenobarbital	Poor (the liver cannot be induced to work) [4] [5]	Good: phenobarbital prevents bilirubin buildup [1] [4]
Definitive treatment	Liver transplant, usually before adolescence [1]	Often lifelong medication and phototherapy
Brain damage risk	High if untreated in the first months of life	Lower with early treatment

Type 1 carries a poorer prognosis if it is not diagnosed and treated within the first few months of life [1]. Children who go untreated are at risk of life-threatening symptoms that may prevent them from living beyond two years of age [1]. Type 2, by contrast, has a good prognosis when treated early [1].

Who Does Crigler-Najjar Syndrome Affect?

The condition can affect anyone because it is genetic. A child inherits it only when both parents pass on a copy of the mutated UGT1A1 gene, a pattern known as autosomal recessive inheritance [1] [3]. If only one parent passes on the mutated gene, the child typically does not develop Crigler-Najjar syndrome [1]. Instead, a single mutated copy may cause a much milder condition called Gilbert's syndrome [1] [3].

Because both parents must carry the mutation, couples with a family history of the condition can explore their risk through genetic counseling and testing before pregnancy.

How does Crigler-Najjar syndrome affect the body?

When red blood cells complete their life cycle, they release bilirubin in its unconjugated (toxic) form. A healthy liver converts this into conjugated (nontoxic) bilirubin, which is then eliminated in stool [1]. The UGT1A1 gene creates the liver enzymes responsible for this conversion [1] [3]. When the gene is mutated, the conversion cannot happen. The toxic form of bilirubin accumulates in the blood and tissues, producing the hallmark yellow tint to skin and eyes [1]. If levels rise high enough, bilirubin deposits in the brain and nerves, a dangerous complication called kernicterus [1].

Step	Healthy process	In Crigler-Najjar syndrome
Red blood cells age	Cells reach end of lifespan	Same; the difference starts in the liver
Bilirubin released	Unconjugated (toxic) bilirubin forms	Same; toxic bilirubin forms normally
Liver processing	UGT1A1 enzymes convert it to the nontoxic form	Conversion fails; toxic form collects
Elimination	Nontoxic bilirubin removed in stool	Bilirubin stays in blood and tissues
Visible effect	No jaundice	Persistent yellowing of skin and eyes
Complication risk	None	Brain damage (kernicterus) if untreated

Normal newborn jaundice is common because newborn livers are not fully developed, and it usually resolves within the first week of life. Children with Crigler-Najjar syndrome have jaundice that persists beyond the newborn period [1]. This is the key difference that raises suspicion.

What are the symptoms and warning signs of Crigler-Najjar syndrome?

Symptoms of Crigler-Najjar syndrome vary in severity depending on the type. The earliest and most consistent sign is persistent jaundice. The dangerous complication, kernicterus, typically appears after one month of age or into early childhood [1]. It can also occur later in life if treatment stops or another illness interrupts treatment progress [1].

Symptom category	Signs to watch for
Visible sign	Persistent yellow skin and eyes (jaundice) beyond the newborn period [1]
Mild kernicterus	Clumsiness, muscle spasms, sensory perception problems, fine motor trouble (grasping objects, fastening buttons), twisting or squirming movements (choreoathetosis), underdeveloped tooth enamel [1]
Severe kernicterus	Hearing difficulty, extreme fatigue (lethargy), feeding difficulties, fever, nausea or vomiting, weak muscle tone (hypotonia) and/or tight muscles (hypertonia), cognitive development problems [1]

Figure 2: Symptoms of Crigler-Najjar syndrome: persistent jaundice and the mild and severe signs of kernicterus.

What Causes Crigler-Najjar Syndrome?

A mutation in the UGT1A1 gene causes Crigler-Najjar syndrome. This gene provides the instructions for liver enzymes that break down bilirubin and remove it from the body [1] [3]. When the gene is mutated, those enzymes cannot function, so toxic unconjugated bilirubin builds up in the blood and tissues instead of being cleared in stool [1].

The condition follows an autosomal recessive inheritance pattern, meaning a child must inherit a mutated copy from both parents [3] [4]. A single inherited copy does not cause Crigler-Najjar syndrome but may produce the much milder Gilbert's syndrome [2] [3]. Because the cause is entirely genetic, there is no lifestyle or environmental factor that triggers or prevents the condition.

How Is Crigler-Najjar Syndrome Diagnosed?

Healthcare providers consider Crigler-Najjar syndrome when a baby has jaundice with a higher bilirubin level than expected for the newborn period, or when jaundice develops rapidly within the first few days to weeks after birth [1] [4]. A physical exam is combined with several tests [1].

Diagnostic test	What it checks
Bilirubin blood test	Measures how much bilirubin is in the blood [1]
Liver function test and complete blood count	Determines how much unconjugated bilirubin is in the blood and stool [1]
Genetic testing	Identifies the mutated UGT1A1 gene responsible for symptoms [1] [4]
Family history review	Looks for a history of genetic conditions to pinpoint the diagnosis before testing [1]

Early diagnosis matters. The sooner the condition is identified and treated, the better the chance of preventing irreversible brain damage.

How is Crigler-Najjar syndrome treated?

Treatment focuses on one central goal: lowering bilirubin levels in the body [1]. The approach depends on the type and severity of the condition.

Treatment	How it works	Best for
Phototherapy	Bright lights help move bilirubin out of the body as waste [1]; protective eyewear is worn while skin is exposed	Ongoing management for both types
Phenobarbital	Prevents bilirubin from building up in the blood (hyperbilirubinemia) [1]	Type 2, where it is effective [1] [4]
Plasmapheresis	Removes plasma containing toxic substances and replaces it with healthy donor plasma [1]	Severe episodes and emergencies
Infection treatment	Medicine for infections or illnesses that cause fever [1], which can worsen bilirubin levels	Supportive care during illness
Liver transplant	A donor's healthy liver replaces the affected liver so bilirubin can be broken down [1]	Type 1, usually before adolescence [1]

Studies show a liver transplant can effectively cure Crigler-Najjar syndrome: replacing a liver that cannot break down bilirubin with one that can prevents life-threatening complications such as brain damage [1].

Figure 3: How Crigler-Najjar syndrome is treated, from phototherapy and phenobarbital to plasmapheresis and liver transplant.

Phototherapy Side Effects and Limitations

Phototherapy is very effective, but it carries trade-offs. Exposure to fluorescent light or sunlight can increase ultraviolet radiation exposure, which raises the risk of skin cancer [1]. Newer LED blue-light technology reduces ultraviolet exposure and is considered the safest option [1]. Phototherapy can also lose effectiveness as a child grows. Increased body mass thickens the skin, making it harder for light to reach bilirubin molecules deeper in the body [1].

Caring for a Child During Treatment

Infants typically sleep under phototherapy lights anywhere from a few times a week to a few times a month. Putting a child to sleep under bright lights, even with light-blocking eye protection, can be difficult at first. Comfort measures like talking to the child or gentle touch help until they adjust. Proper hydration is essential throughout treatment.

What is the outlook for Crigler-Najjar syndrome?

With early treatment, children with Type 2 have a good prognosis [1]. Children with Type 1 face a much poorer outlook if the condition is not diagnosed and treated within the first few months of life [1]. Most people with either type need lifelong treatment and management, and with effective treatment, they can have a normal lifespan [1].

Scenario	Expected outcome
Type 2, treated early	Good prognosis; normal life expectancy [1]
Type 1, treated in first months	Reduced risk of life-threatening symptoms; transplant often curative
Type 1, untreated or late-diagnosed	Risk of fatal complications; may not survive past two years [1]
After liver transplant	Effective cure; prevention of brain damage [1]

When should you see a provider about Crigler-Najjar syndrome?

Crigler-Najjar syndrome can cause irreversible, life-threatening symptoms, so prompt care matters. Contact your child's provider if you notice symptoms affecting their ability to thrive.

Warning sign	Why it matters
Jaundice that will not go away after phototherapy	Bilirubin levels remain dangerously high
High fever	Illness and fever can worsen bilirubin buildup
Trouble eating	Feeding difficulties may signal kernicterus
Developmental delays	May indicate early brain involvement

Caretakers should also remember their own wellbeing. A rare genetic diagnosis is stressful, and speaking with a mental health professional helps parents care for their child at their best.

Questions to Ask Your Provider

Question	Why it matters
How long will my child need phototherapy?	Determines the ongoing treatment schedule
Are there side effects to the recommended treatment?	Helps weigh phototherapy UV exposure and alternatives
Does my child need a liver transplant?	Clarifies whether definitive surgery is the right path
How serious is my child's diagnosis?	Establishes the type and prognosis
Can phototherapy be done at home?	Affects daily routine and family life

Conclusion

Crigler-Najjar syndrome is a rare genetic condition that leaves the liver unable to break down toxic bilirubin, causing persistent jaundice in newborns and young children. Type 1 is severe and life-threatening without early intervention, usually a liver transplant performed before adolescence [1], while Type 2 is milder and responds well to phenobarbital and phototherapy [1] [2]. The greatest danger is kernicterus, irreversible brain damage caused by bilirubin accumulating in the brain, which is why early diagnosis and consistent treatment are essential. Most people with the condition need lifelong management, and with effective treatment, they can live a normal lifespan [1]. A liver transplant offers a functional cure.

If your newborn has jaundice that persists beyond the first week of life, talk to a pediatrician about bilirubin testing and genetic evaluation. If you have a family history of the condition, explore genetic counseling before pregnancy.

Frequently Asked Questions

1. What is Crigler-Najjar syndrome?

Crigler-Najjar syndrome is a rare genetic condition in which the liver cannot break down bilirubin, a toxic byproduct of red blood cell turnover. The buildup causes persistent jaundice and, if untreated, irreversible brain damage. It affects fewer than 1 in 1 million newborns worldwide.

2. What causes Crigler-Najjar syndrome?

A mutation in the UGT1A1 gene, which normally creates the liver enzymes that convert toxic bilirubin into its nontoxic form. The condition is autosomal recessive: a child must inherit a mutated copy from both parents.

3. What is the difference between type 1 and type 2?

Type 1 is severe and life-threatening, often requiring a liver transplant before adolescence; many untreated children do not survive past childhood. Type 2 is milder, responds to phenobarbital, and typically allows a normal life expectancy.

4. What are the symptoms of Crigler-Najjar syndrome?

The main sign is persistent jaundice (yellow skin and eyes) beyond the newborn period. Severe bilirubin buildup causes kernicterus, with symptoms including hearing difficulty, feeding problems, extreme fatigue, fever, muscle tone abnormalities, and developmental delays.

5. What is kernicterus?

Kernicterus is brain damage caused when excess bilirubin deposits in the brain and nerves. It is life-threatening and irreversible, typically appearing after one month of age or into early childhood if the condition is untreated.

6. Is Crigler-Najjar syndrome hereditary?

Yes. It follows an autosomal recessive pattern, so both parents must carry the mutated UGT1A1 gene. A single inherited copy may instead cause the much milder Gilbert's syndrome.

7. How is Crigler-Najjar syndrome diagnosed?

Through bilirubin blood tests, liver function tests, complete blood counts, and genetic testing to identify the UGT1A1 mutation. Providers also review family history of genetic conditions before testing.

8. How is Crigler-Najjar syndrome treated?

Treatment lowers bilirubin levels through phototherapy (bright lights that help remove bilirubin through the skin), phenobarbital (effective for type 2), plasmapheresis for acute episodes, and liver transplant, a functional cure typically recommended for type 1 before adolescence.

9. Is there a cure for Crigler-Najjar syndrome?

A liver transplant is considered a cure. Replacing the affected liver with a healthy donor liver restores the body's ability to break down bilirubin and prevents life-threatening complications like brain damage.

10. Can Crigler-Najjar syndrome be prevented?

No. It is a genetic condition, so it cannot be prevented. Couples with a family history can pursue genetic testing and counseling before pregnancy to understand their risk.

11. What is the long-term outlook?

Most people need lifelong treatment and management. With effective treatment, children with type 2 have a normal life expectancy, and those with type 1 can achieve a normal lifespan after transplant. Early diagnosis within the first months of life is critical.

References

1. Cleveland Clinic. Crigler-Najjar Syndrome. Cleveland Clinic. May 3, 2022. https://my.clevelandclinic.org/health/diseases/22949-crigler-najjar-syndrome

2. American Liver Foundation. Crigler-Najjar Syndrome. American Liver Foundation. August 16, 2023. https://liverfoundation.org/liver-diseases/pediatric-liver-information-center/pediatric-liver-disease/crigler-najjar-syndrome/

3. National Library of Medicine. Crigler-Najjar syndrome. MedlinePlus Genetics. February 1, 2012. https://medlineplus.gov/genetics/condition/crigler-najjar-syndrome/

4. National Organization for Rare Disorders (NORD). Crigler Najjar Syndrome. National Organization for Rare Disorders. August 2, 2016. https://rarediseases.org/rare-diseases/crigler-najjar-syndrome/

5. Bhandari J, Thada PK, Shah M, Yadav D. Crigler-Najjar Syndrome. StatPearls (NCBI Bookshelf). February 12, 2024. https://www.ncbi.nlm.nih.gov/books/NBK562171/

6. Dhawan A, Lawlor MW, Mazariegos GV, et al. Disease burden of Crigler-Najjar syndrome: systematic review and future perspectives. J Gastroenterol Hepatol. 2020;35(4):530-543. doi:10.1111/jgh.14853. PMID: 31495946.

7. Sambati V, Laudisio S, Motta M, Esposito S. Therapeutic options for Crigler-Najjar syndrome: a scoping review. Int J Mol Sci. 2024;25(20):11006. doi:10.3390/ijms252011006. PMID: 39456788.

8. D'Antiga L, Beuers U, Ronzitti G, et al. Gene therapy in patients with the Crigler-Najjar syndrome. N Engl J Med. 2023;389(7):620-631. doi:10.1056/NEJMoa2214084. PMID: 37585628.

Medical Disclaimer

This article is for informational purposes only and does not constitute medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read here.