Crigler-Najjar syndrome

What is Crigler-Najjar syndrome?

Crigler-Najjar syndrome is a rare genetic disorder that affects how your liver processes bilirubin. Bilirubin is a yellow substance created when your body breaks down old red blood cells. Normally, your liver converts bilirubin into a form that can be easily removed through bile and waste. People with this condition lack or have reduced amounts of an enzyme called UGT1A1, which is needed for this conversion.

Without enough of this enzyme, bilirubin builds up in the blood and tissues. This causes a type of jaundice where the skin and eyes turn yellow. There are two types of Crigler-Najjar syndrome. Type 1 is the more severe form where the enzyme is completely absent. Type 2 is milder because some enzyme activity remains.

This condition is inherited in an autosomal recessive pattern. That means both parents must carry the gene mutation for a child to develop the syndrome. Crigler-Najjar syndrome affects roughly 1 in 1 million people worldwide. Early diagnosis and ongoing care are essential to prevent serious complications from high bilirubin levels.

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Symptoms

Severe jaundice, yellowing of the skin and whites of the eyes, appearing in newborns within the first few days of life
Dark urine that may appear yellow or brown in color
Pale or light-colored stools
In Type 1, risk of kernicterus, a type of brain damage caused by very high bilirubin levels
Poor feeding or lethargy in infants with severe cases
Muscle spasms or abnormal movements if bilirubin affects the brain
Developmental delays in untreated severe cases
In Type 2, milder jaundice that may worsen during illness or stress

Type 1 symptoms are typically more severe and appear immediately after birth. Type 2 may have milder symptoms that can sometimes go undetected in early infancy. Both types require medical attention to prevent long-term complications.

Causes and risk factors

Crigler-Najjar syndrome is caused by mutations in the UGT1A1 gene. This gene provides instructions for making an enzyme that helps convert bilirubin into a water-soluble form. When the gene is mutated, the enzyme either does not work at all or works poorly. In Type 1, the enzyme is completely absent. In Type 2, the enzyme has reduced activity but is still partially functional.

The condition is inherited in an autosomal recessive pattern. Both parents must carry one copy of the mutated gene for their child to have the syndrome. Carriers typically have no symptoms themselves. There are no lifestyle or environmental risk factors that cause this condition. Family history is the primary risk factor, especially in communities where consanguineous marriage is more common.

How it's diagnosed

Crigler-Najjar syndrome is diagnosed through blood tests that measure bilirubin levels. Total bilirubin levels are significantly elevated, often above 20 mg/dL in Type 1 and between 6 to 25 mg/dL in Type 2. Liver function tests are typically normal, which helps distinguish this condition from other liver diseases. Genetic testing can confirm mutations in the UGT1A1 gene and identify the specific type.

Doctors may also perform a phenobarbital trial to differentiate between Type 1 and Type 2. In Type 2, phenobarbital medication can lower bilirubin levels. In Type 1, it has no effect. Monitoring bilirubin levels is essential for ongoing care. If you suspect you or your child has symptoms of this condition, talk to a doctor about specialized testing. Our team can help you understand your bilirubin results and connect you with appropriate care.

Treatment options

Phototherapy, light therapy that helps break down bilirubin in the skin, used daily for Type 1 patients
Phenobarbital medication for Type 2 to help lower bilirubin levels
Liver transplant, the only definitive cure for Type 1, typically considered in severe cases
Avoiding medications and substances that can increase bilirubin levels, such as certain antibiotics
Preventing infections and illness, which can trigger bilirubin spikes
Regular monitoring of bilirubin levels through blood tests
In some cases, plasmapheresis or exchange transfusions to rapidly reduce dangerously high bilirubin
Gene therapy and enzyme replacement therapy are being researched as future treatment options
Working with a specialist in metabolic or genetic disorders for personalized care plans

Frequently asked questions

Type 1 is the more severe form where the UGT1A1 enzyme is completely absent. Bilirubin levels are very high and do not respond to medication. Type 2 is milder because some enzyme activity remains. Bilirubin levels are lower and can be reduced with phenobarbital medication.

Liver transplant is currently the only cure for Type 1 Crigler-Najjar syndrome. It replaces the liver with one that has functioning UGT1A1 enzyme. Type 2 can often be managed with medication and does not typically require transplant. Research into gene therapy and enzyme replacement offers hope for future treatment options.

The condition is inherited in an autosomal recessive pattern. Both parents must carry one copy of the mutated UGT1A1 gene. Each child of two carriers has a 25% chance of having the syndrome, a 50% chance of being a carrier, and a 25% chance of inheriting two normal genes.

Normal total bilirubin levels are typically below 1.2 mg/dL in adults. In Type 1 Crigler-Najjar syndrome, levels are usually above 20 mg/dL and can reach as high as 50 mg/dL. Type 2 typically shows levels between 6 and 25 mg/dL.

Phototherapy is effective for managing Type 1 but is not a cure. Patients typically need 10 to 12 hours of light therapy daily throughout their lives. The light helps convert bilirubin in the skin into forms that can be excreted more easily. As patients grow larger, phototherapy becomes less effective because light cannot penetrate deeper tissues.

Kernicterus is a type of brain damage caused by very high levels of bilirubin. It occurs when bilirubin crosses the blood-brain barrier and deposits in brain tissue. This can cause permanent neurological damage including hearing loss, movement disorders, and developmental delays. Preventing kernicterus is the primary goal of treatment in Type 1 Crigler-Najjar syndrome.

Crigler-Najjar syndrome is present from birth because it is a genetic condition. However, Type 2 may not be diagnosed until later in childhood or even adulthood if symptoms are mild. The condition does not develop later in life, but diagnosis can be delayed in less severe cases.

Illness, infection, stress, fasting, and certain medications can all cause bilirubin levels to rise. Dehydration can also worsen jaundice. People with Crigler-Najjar syndrome need to manage these triggers carefully and seek medical care promptly during illness to prevent dangerous bilirubin elevations.

Monitoring frequency depends on the type and severity of the condition. People with Type 1 may need weekly or monthly testing, especially during childhood. Those with Type 2 on stable medication may only need testing every few months. During illness or when starting new treatments, more frequent testing is necessary.

With proper management, many people with Type 2 can live relatively normal lives with medication. Type 1 requires daily phototherapy and careful monitoring, which impacts daily routines. Liver transplant can significantly improve quality of life for Type 1 patients. Early diagnosis and consistent treatment are key to preventing complications and maintaining the best possible health.