Crigler-Najjar Syndrome (CNS)
Crigler-Najjar syndrome (CNS) is an inherited disease in which bilirubin (a pigment produced in the liver during the breakdown of red blood cells) cannot be properly broken down by the liver. In CNS, a specific enzyme responsible for the breakdown of bilirubin malfunctions.
According to Genetics Home Reference, a publication of the National Institutes of Health (NIH), CNS is an extremely rare disorder seen in only one of every 1,000,000 births (GeneticsHomeReference, 2012).
There are two types of CNS: type 1 and type 2. Type 1 (early-onset CNS) is a severe form of the disorder and most patients do not survive childhood. Type 2 (late-onset CNS) is less severe and many patients with this form survive into adulthood.
How Does Crigler-Najjar Syndrome (CNS) Develop?
Enzymes are proteins that are essential to the normal functioning of many body systems and the chemical reactions that regulate the body’s many systems. In CNS, the enzyme that typically breaks down bilirubin fails to work adequately, causing the bilirubin to build up in the body.
Crigler-Najjar is an inherited disease. If either of your parents or any grandparents had CNS, you are more likely to develop the condition. You must inherit a defective gene from both parents to get the severe form.
What Are the Signs of Crigler-Najjar Syndrome (CNS)?
As bilirubin builds up, the skin and eyes turn yellow, leading to a condition known as jaundice. This yellowing is usually apparent at birth or soon after and is the most visible and striking sign of CNS. The yellowing often becomes more pronounced as bilirubin increases.
In addition to yellowed skin and eyes, a baby with jaundice may be:
- hard to wake up
- unable to sleep
- unable to urinate or defecate
Untreated jaundice causes kernicterus. Kernicterus is a form of brain damage, which can lead to:
- athetoid cerebral palsy (a form of cerebral palsy involving involuntary movement of the hands, arms, and legs)
- hearing loss
- vision problems
- intellectual disability
Seek medical attention immediately if your child shows any signs of jaundice or possible CNS.
Diagnosing Crigler-Najjar Syndrome (CNS)
Several factors play a part in diagnosing CNS. Your doctor could run several tests and ask questions about family history to make the correct diagnosis.
Your doctor may use your past medical history, family history, and a blood test to determine if the condition is present. A blood sample can be checked for the presence of bilirubin. The bilirubin in the blood is measured to determine if CNS is present.
In infants, an initial bilirubin test is administered using a light meter. By holding the light meter to a child’s head, a nurse can check the bilirubin levels present in the skin. A high bilirubin result is usually indicative of jaundice. If the level is high, the doctor will likely order a blood test.
Other tests that may be used to measure bilirubin or the functioning of the liver include a liver biopsy (a small piece of the liver is removed and examined under a microscope) and an enzyme assay (measurement of enzyme activity).
Treating Crigler-Najjar Syndrome (CNS)
There are multiple possible courses of treatment for CNS. The foremost treatments are described in the following sections.
The most common treatment for babies with CNS is light therapy, also known as phototherapy. This noninvasive procedure exposes the child’s skin to blue light to prevent or treat yellowing of the skin. This treatment is more successful in children, due to their skin being much thinner. Thin skin makes it easier for light to be absorbed. Adults have thicker skin that does not allow light to be as readily absorbed.
In serious cases, a blood transfusion may be necessary to remove excess bilirubin from your bloodstream. A blood transfusion works by removing a measured amount of blood through one tube, while feeding fresh blood into your body through another tube. It is typically done in an outpatient setting and takes one to two hours.
People with early-onset (type 1) CNS may find success in having a liver transplant. However, this option isn’t successful in people with late-onset CNS.
People with late-onset CNS may be treated using a drug called phenobarbital. This medication is normally prescribed to people who suffer from seizures, but it is also prescribed to treat the symptoms of CNS. This is a habit-forming drug, so it is usually used under close monitoring by your doctor.
Long-Term Outlook for Crigler-Najjar Syndrome (CNS Patients)
Patients with type 2 (late-onset) CNS have a better outlook. People with type 2 CNS do not suffer significant organ damage. However, they may develop jaundice.
Children with type 1 CNS need lifelong treatment for this syndrome. If they survive, children with this form of the syndrome typically have significant brain damage as adults.