Defects of Bilirubin UDP-Glucuronosyltransferase

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What are the three major processes involved in the transfer of bilirubin from blood to bile?

Uptake, conjugation, and secretion

Which specific enzymes are responsible for removing glucuronosyl moieties from conjugated bilirubin in the intestines?

Bacterial β-glucuronidases

What is the group of colorless tetrapyrroles formed by the reduction of urobilinogens by fecal flora?

Urobilinogens

What is the role of Bilirubin UDP-Glucuronosyltransferase enzymes?

Increase the polarity of various drugs and drug metabolites for excretion Signup and view all the answers

In which part of the body does the reabsorption of small portions of urobilinogens occur?

Terminal ileum and large intestine Signup and view all the answers

How do mutations in the gene encoding bilirubin UDP-glucuronosyltransferase affect enzyme activity?

Result in reduced or absent activity Signup and view all the answers

Under what conditions may urobilinogen be excreted in the urine?

When excessive bile pigment is formed or when liver disease disrupts the intrahepatic cycle Signup and view all the answers

Name two syndromes associated with impaired bilirubin conjugation.

Gilbert syndrome and Crigler-Najjar syndrome Signup and view all the answers

What can cause unconjugated hyperbilirubinemia?

Toxin-induced liver dysfunction by substances like acetaminophen or hepatitis virus Signup and view all the answers

Name a syndrome related to impaired bilirubin conjugation that results in toxic jaundice.

Crigler-Najjar syndrome Signup and view all the answers

What is the most common cause of conjugated hyperbilirubinemia?

Obstruction in the biliary tree, often due to gallstones or pancreatic cancer Signup and view all the answers

What happens when bilirubin diglucuronide cannot be excreted properly?

It regurgitates into the hepatic veins and lymphatics, leading to choluric jaundice Signup and view all the answers

What is the main cause of predominantly conjugated hyperbilirubinemia in liver diseases?

Liver diseases, such as hepatitis Signup and view all the answers

What is the usual level of bilirubin in hyperbilirubinemia despite extensive hemolysis?

Less than 4 mg/dL Signup and view all the answers

What is the maximum level of serum bilirubin that toxic hyperbilirubinemia tends not to exceed?

20 mg/dL Signup and view all the answers

What is the result of accelerated hemolysis and an immature hepatic system in neonatal 'physiologic jaundice'?

Unconjugated hyperbilirubinemia Signup and view all the answers

What can happen if the plasma concentration of unconjugated bilirubin exceeds the binding capacity of albumin in neonates?

Bilirubin can penetrate the blood-brain barrier Signup and view all the answers

What can untreated hyperbilirubinemia in neonates lead to?

Hyperbilirubinemic toxic encephalopathy or kernicterus Signup and view all the answers