High levels of bilirubin, or hyperbilirubinemia, can be seen in numerous diseases. Bilirubin is a yellowish pigment that is a byproduct of the degeneration and recycling of old red blood cells. The pigment also grants color to the urine and feces produced by the patient's excretory pathways. High levels of bilirubin can cause the skin to appear yellow---a condition called jaundice---and lead to damage of the nervous system and brain. Understanding the causes of hyperbilirubinemia will help in the diagnosis and treatment of the condition.
Abnormal Blood Cell Structure
If red blood cells are deformed, then the patient may develop high levels of bilirubin, states MedlinePlus, a National Institutes of Health website. Red blood cells are usually bi-concave in shape, but in certain congenital conditions the cells become structurally abnormal. Conditions such as congenital spherocytic anemia, sickle cell disease and elliptocytosis can change the shape of red blood cells. Abnormally shaped red blood cells are easily destroyed as they travel through the circulatory system. As these cells rupture, they release large amounts of bilirubin that stay within the system, reports Elmhurst College, of Elmhurst, Illinois. This causes hyperbilirubinemia.
Crigler-Najjar Syndrome
Crigler-Najjar syndrome is a genetic disease that can cause hyperbilirubinemia. A pair of abnormal genes within the patient's DNA is responsible for the production of an abnormal enzyme, reports "The New York Times" Health Guide. Without a normal enzyme, the patient is unable to secrete bilirubin. The bilirubin builds up in the patient's body and leads to jaundice and hyperbilirubinemia. Crigler-Najjar that presents early in life is known as type 1, and if it occurs later in life, it is called type 2. Symptoms of this disease include jaundice, confusion and behavioral changes.
Physiologic Jaundice
In most newborns, the skin will appear slightly yellow. This condition is called physiologic jaundice and is a normal finding in healthy newborns, according to KidsHealth.org. The infant's liver is still immature and is unable to effectively eliminate all of the bilirubin produced by the body. This leads to slightly elevated levels of bilirubin in the neonate. The high levels of bilirubin begin two or three days after birth, peak by day four and then return to normal by the second week of life, reports MedlinePlus. Typically, there are no severe long-term complications of physiologic jaundice.
Bile Duct Obstruction
The liver excretes excess bilirubin as bile. Bile is produced in the liver and then transported to the gallbladder or intestines for removal from the body. In order to reach the intestines, the bile must pass through the bile duct. If the bile duct becomes blocked or obstructed, bile, and hence bilirubin levels, increase within the body, according to the University of Maryland Medical Center. The bile duct can become obstructed by cysts within the duct, bile duct cancer, gallstones, trauma from surgery and abnormal inflammation of the tissues lining the bile duct.
