E80.5 Crigler-Najjar syndrome

Name of the Condition

• Crigler-Najjar syndrome

Summary

Crigler-Najjar syndrome is a rare inherited disorder affecting bilirubin metabolism, characterized by severe unconjugated hyperbilirubinemia (high levels of indirect bilirubin) due to a deficiency in the enzyme uridine diphosphate-glucuronosyltransferase (UGT1A1). This condition impairs the liver’s ability to process bilirubin, leading to its accumulation in the blood and tissues. It is classified into two types based on enzyme activity and clinical severity.

Causes

The syndrome is caused by genetic mutations in the UGT1A1 gene, which encodes the UGT1A1 enzyme responsible for bilirubin conjugation. Type 1 results from complete absence of enzyme activity, while Type 2 involves reduced but residual activity. These mutations are typically inherited in an autosomal recessive pattern, meaning both parents must carry a copy of the mutated gene for the condition to manifest.

Risk Factors

• Genetic inheritance of UGT1A1 mutations from both parents.
• Family history of Crigler-Najjar syndrome or related bilirubin metabolism disorders.
• Newborns or infants, as symptoms often present shortly after birth.

Symptoms

• Severe jaundice (yellowing of skin and eyes) appearing in the first days of life.
• Dark urine due to bilirubin excretion.
• Potential neurological symptoms (e.g., lethargy, seizures) in severe cases if bilirubin levels become extremely high (kernicterus).

Diagnosis

Diagnosis involves measuring serum bilirubin levels, which show predominantly unconjugated bilirubin. Liver function tests are typically normal, distinguishing it from other causes of jaundice. Genetic testing confirms UGT1A1 mutations, and a liver biopsy may be performed to assess enzyme activity. The absence of hemolysis (breakdown of red blood cells) further supports the diagnosis.

Treatment Options

Treatment focuses on reducing bilirubin levels to prevent neurological damage. Phototherapy (light therapy) is used to help the body eliminate bilirubin. For Type 1, liver transplantation may be necessary. Experimental therapies, such as enzyme replacement or gene therapy, are under investigation. Close monitoring of bilirubin levels is critical.

Prognosis and Follow-Up

Prognosis depends on the type and timeliness of treatment. Type 1 has a poor prognosis without intervention, as high bilirubin levels can lead to irreversible brain damage. Type 2 has a better prognosis with milder symptoms and may respond to phenobarbital to induce enzyme activity. Lifelong monitoring of bilirubin levels and neurological status is essential.

Complications

• Kernicterus (bilirubin-induced brain damage) leading to neurological impairment or death.
• Developmental delays or intellectual disability if untreated.
• Increased risk of gallstones due to chronic bilirubin elevation.

Lifestyle & Prevention

• Avoid medications that may exacerbate jaundice or liver function.
• Protect infants from excessive sun exposure, as phototherapy is a key treatment.
• Genetic counseling for families with a history of the syndrome to assess recurrence risk.

When to Seek Professional Help

Seek immediate medical attention if an infant shows signs of jaundice (yellow skin/eyes), lethargy, or poor feeding, as early intervention is critical to prevent complications. Regular follow-up with a hepatologist or geneticist is recommended for ongoing management.

Tips for Medical Coders

Document the specific type of Crigler-Najjar syndrome (Type 1 or Type 2) when available, as this may impact coding specificity. Note any associated complications, such as kernicterus, and document the use of phototherapy or liver transplantation, as these details support accurate code assignment. Ensure laboratory results (e.g., bilirubin levels, genetic test findings) are included in the record to confirm the diagnosis.