Crigler Najjar Syndrome: Early Signs, Risk Factors, and How It Is Treated

Crigler Najjar syndrome is a rare genetic liver condition in which the body cannot process bilirubin normally, leading to persistent jaundice soon after birth. Early diagnosis and specialist care are important because very high bilirubin levels can affect the brain, particularly in the more severe form of the condition.

Overview: What Is Crigler Najjar Syndrome?

Crigler Najjar syndrome is a rare inherited condition that causes high levels of unconjugated bilirubin in the blood. Bilirubin is a yellow substance made when old red blood cells are broken down. Normally, the liver changes bilirubin into a form that can leave the body in stool. In this syndrome, the liver cannot complete this step effectively.

As bilirubin builds up, the skin and whites of the eyes become yellow, a finding called jaundice. Unlike many common forms of newborn jaundice, Crigler Najjar syndrome causes jaundice that is marked, persistent, or both. The condition is present from birth and needs assessment by clinicians experienced in neonatal jaundice and inherited liver disorders.

There are two main forms. Type 1 causes little to no bilirubin-processing enzyme activity and is the more serious form. Type 2 involves reduced, rather than absent, enzyme activity and is usually less severe. Both forms require ongoing medical follow-up, but their management and long-term outlook differ.

Early Signs and Symptoms

Jaundice is the main early sign of Crigler Najjar syndrome. It usually appears during the first days of life and remains noticeable rather than improving over time. The yellow color may be seen first in the face and eyes, then become more widespread. Blood tests show elevated unconjugated bilirubin, while many other liver test results may be normal.

Babies may otherwise seem well at first, feeding and growing normally. This can make it especially important not to assume that prolonged or intense newborn jaundice is harmless. A clinician should assess jaundice promptly, particularly when it appears in the first 24 hours after birth, is deepening, persists beyond the expected newborn period, or occurs alongside poor feeding or unusual sleepiness.

Very high unconjugated bilirubin can cross into brain tissue and cause bilirubin neurotoxicity, also called kernicterus. Warning signs may include poor feeding, lethargy, a high-pitched cry, changes in muscle tone, arching of the neck or back, or unusual movements. These signs require urgent emergency assessment. With careful bilirubin control, the risk can be substantially reduced.

Why It Happens and Who Is at Risk

Crigler Najjar syndrome results from changes in the UGT1A1 gene. This gene provides instructions for making an enzyme called UDP-glucuronosyltransferase, often shortened to UGT1A1. The enzyme helps convert unconjugated bilirubin into conjugated bilirubin, which can then be removed from the body through bile and stool.

The condition is usually inherited in an autosomal recessive pattern. This means an affected child generally receives one altered copy of the relevant gene from each parent. Parents who carry one altered copy usually do not have Crigler Najjar syndrome themselves. When both parents are carriers, each pregnancy may carry a chance of having an affected child, being a carrier, or inheriting no altered copy.

Crigler Najjar syndrome is not caused by diet, infection, parenting, or routine activities during pregnancy. It is distinct from more common temporary newborn jaundice and from Gilbert syndrome, another UGT1A1-related condition that typically causes mild, intermittent bilirubin elevation later in life. Genetic counseling may help families understand inheritance, testing options, and implications for future pregnancies.

How Doctors Diagnose It

Diagnosis begins with an urgent evaluation of jaundice and a blood test to measure total and direct bilirubin. In Crigler Najjar syndrome, the indirect or unconjugated portion is markedly elevated. Clinicians also assess the baby’s age, feeding, weight change, medical history, family history, and physical examination findings.

Because many conditions can cause jaundice, doctors may order tests to rule out other causes. These can include a complete blood count, blood group and antibody testing, tests for red blood cell breakdown, thyroid testing, infection assessment when indicated, and liver-related blood tests. Stool and urine color may also provide useful clues, because disorders that block bile flow tend to produce a different bilirubin pattern.

Genetic testing can identify changes in the UGT1A1 gene and support a diagnosis. The degree of bilirubin elevation, response to treatment, and genetic findings can help distinguish Type 1 from Type 2. A pediatric hepatologist, metabolic specialist, neonatologist, or clinical geneticist may be involved in confirming the diagnosis and planning care.

Treatment Options and Ongoing Care

Treatment aims to lower unconjugated bilirubin and protect the brain from bilirubin toxicity. In newborns with very high bilirubin, care may need to begin immediately while testing is underway. Intensive blue-light phototherapy changes bilirubin in the skin into forms that can be eliminated without the usual liver processing step. Babies may require prolonged daily phototherapy and close monitoring of hydration, feeding, temperature, skin, and bilirubin levels.

Type 1 Crigler Najjar syndrome usually does not respond meaningfully to phenobarbital, a medicine that can increase residual UGT1A1 activity in some people. For Type 1, liver transplantation is considered the definitive treatment because the new liver can process bilirubin normally. Timing is individualized and depends on bilirubin control, treatment burden, neurological risk, and the person’s overall health.

In Type 2, phenobarbital may lower bilirubin levels because some enzyme activity remains. Phototherapy may still be useful, especially in infancy, during illness, or when bilirubin rises. People with either type need an individualized plan for monitoring, including plans for infections, dehydration, fasting, or other stresses that may increase bilirubin. Research into cell-based and gene-based treatments is ongoing, but these approaches are not yet standard care.

Daily Management, Prevention, and Family Planning

Because Crigler Najjar syndrome is genetic, it cannot currently be prevented through lifestyle changes. However, bilirubin-related complications can often be prevented or reduced through early diagnosis, consistent treatment, and a clear follow-up plan. Families may be taught how to use home phototherapy equipment safely when this is appropriate and how to recognize signs that require urgent assessment.

Regular feeding and good hydration are particularly important for infants and young children. Parents and caregivers should avoid delaying medical review when a child is unwell, feeding poorly, vomiting, has diarrhea, or seems unusually sleepy. Clinicians should also review new medicines carefully, since some medicines may affect bilirubin handling or be unsuitable for an individual child.

Genetic counseling can be valuable after diagnosis. It can explain carrier testing for relatives and discuss reproductive options in a non-directive way. Families may also benefit from coordinated support involving pediatric liver specialists, dietitians, nurses, transplant teams where needed, and mental health or social support professionals.

When to Seek Medical Care

Newborn jaundice should always be discussed with a healthcare professional, especially if it begins within the first day after birth, becomes more intense, spreads to the legs, lasts longer than expected, or is accompanied by feeding difficulties. Prompt testing is particularly important when there is a family history of severe newborn jaundice, Crigler Najjar syndrome, unexplained infant neurological problems, or known UGT1A1 variants.

Emergency medical care is needed if a baby or child with jaundice is very sleepy or difficult to wake, refuses feeds, has a high-pitched cry, develops fever, arches the back or neck, becomes floppy or unusually stiff, or has seizures. These symptoms do not always indicate bilirubin toxicity, but they need urgent assessment.

People already diagnosed with Crigler Najjar syndrome should attend scheduled specialist appointments and follow their personalized bilirubin management plan. Acibadem International’s multidisciplinary specialists and JCI-accredited hospitals can assess and treat inherited liver conditions for international patients, including coordination of pediatric, genetic, and transplant-related care when appropriate.

Frequently asked questions

Is Crigler Najjar syndrome curable?

Liver transplantation is considered a definitive treatment for Type 1 Crigler Najjar syndrome because it provides a liver with normal bilirubin-processing ability. Before transplantation, intensive phototherapy is commonly used to control bilirubin. Type 2 may often be managed with medicine and monitoring, although care remains lifelong.

What is the difference between Type 1 and Type 2 Crigler Najjar syndrome?

Type 1 involves almost complete absence of UGT1A1 enzyme activity, causing very high bilirubin levels and a greater risk of neurological complications. Type 2 retains some enzyme activity, so bilirubin levels are usually lower. Type 2 may respond to phenobarbital, while Type 1 generally does not.

Can Crigler Najjar syndrome be found during pregnancy?

If a family’s disease-causing genetic variants are known, genetic counseling can discuss testing options before or during pregnancy. The available options depend on local regulations, the family’s wishes, and specialist advice. Families may also consider carrier testing for relatives.

Does jaundice always mean a baby has Crigler Najjar syndrome?

No. Jaundice is common in newborns and often has temporary, treatable causes. However, severe, early, persistent, or worsening jaundice needs timely medical evaluation to identify the cause and prevent complications.

Can a person with Crigler Najjar syndrome live into adulthood?

Yes, many people can reach adulthood with consistent specialist care and appropriate bilirubin control. Long-term outlook depends on the type of syndrome, how well bilirubin is managed, whether neurological injury occurred, and access to treatments such as transplantation when needed. Ongoing follow-up remains important throughout life.

Is Crigler Najjar syndrome contagious?

No. Crigler Najjar syndrome is an inherited genetic condition and cannot be passed from person to person. It is not caused by an infection and does not spread through contact, feeding, or everyday family activities.

References

• National Institute of Diabetes and Digestive and Kidney Diseases
• National Organization for Rare Disorders
• MedlinePlus Genetics
• American Academy of Pediatrics
• Orphanet

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.