Jaundice pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Overview

Bilirubin is the catabolic product of the heme which is the main component of the red blood cells. Bilirubin is formed in the liver and spleen then it passes through several process in order to be metabolized. Metabolism processes include hepatic uptake, conjugation, clearance and excretion of the bilirubin in the bile. Jaundice develops due to increase the level of bilirubin and deposition under the skin and cause the yellow discoloration of the skin. Pathogenesis of neonatal jaundice includes physiologic process of bilirubin accumulation or pathological mechanism. The pathological jaundice may be acquired or inherited. Acquired neonatal jaundice include Rh hemolytic disease, ABO incompatibility disease, and hemolytic disease due to G6PD enzyme deficiency. Inherited neonatal jaundice is due to defect of one of the processes of bilirubin metabolism and it concludes some inherited syndromes. Inherited neonatal jaundice include Gilbert's syndrome, Crigler-Najjar syndrome type I and II, Lucey-Driscoll syndrome, Dubin-Johnson syndrome, and Rotor syndrome.

Pathophysiology

Bilirubin formation and metabolism

  • Bilirubin is the final catabolic product of the heme. The heme is a component of various body substances and enzymes but it is mainly incorporated in the hemoglobin which is the main component of the red blood cells.[1][2]
  • Bilirubin is formed mainly in the liver and spleen through two steps which include the following:[3][4]
    • Heme oxygenase enzyme dysregulates the porphyrin ring of the heme and breaks it down. A green substance called biliverdin is then formed as a result of the previous reaction. Carbon monoxide is a result of the reaction as well
    • Biliverdin reductase enzyme catalyzes the formation of bilirubin from biliverdin.
  • Bilirubin is a toxic metabolite so, the body has physiologic processes in order to eliminate the bilirubin. Bilirubin elimination includes the following process:[5]
    • Hepatic uptake:[6]
      • After the formation of the bilirubin and its secretion into the bloodstream, bilirubin becomes bound to the albumin to facilitate its transportation to the liver.
      • The hepatocytes then reuptake the bilirubin and prepare it for excretion.
    • Conjugation:[7][8]
      • Bilirubin is then conjugated with glucuronic acid producing bilirubin diglucuronide which is water soluble.
      • Being water soluble, hence, the conjugated bilirubin can be excreted into bile.
      • The conjugation process occurs by the glucuronosyltransferase enzyme in the liver cells.
    • Clearance and excretion:[9]
      • After conjugation of the bilirubin in the liver, it is secreted into the bile then into the gastrointestinal tract.
      • In the GIT, the conjugated bilirubin is metabolized by the gut enzymes into urobilinogen which is oxidized into urobilin.
      • Metabolism of the conjugated bilirubin occurs properly in the adults. However, the newborns have sterile gastrointestinal canal which impedes the catalyzation of the conjugated bilirubin.
      • The sterile tract will end up with a small amount of excreted bile.
      • The remaining conjugated bilirubin will be unconjugated by the beta-glucuronidase enzyme in the neonatal intestine.
      • The unconjugated bilirubin can be reabsorbed back into the blood and to the liver through the enterohepatic circulation of bilirubin.
      • A small amount of bilirubin is cleared into the urine as urobilinogen.

Pathogenesis

  • Neonatal jaundice may be a result of physiologic or pathological mechanisms. The different mechanisms of developing jaundice are concluded into either an increase in the bilirubin production, or increase the enterohepatic circulation, or decrease bilirubin elimination.[10]
  • Physiological jaundice:[11][12]
    • The child has red blood cells twice or more than what the adults have and with shorter lifespan.
    • Increase rate of the red blood cells destruction produces more levels of bilirubin which end up with jaundice.
    • The newborn gastrointestinal gut is considered sterile so, a little amount of the unconjugated is converted to conjugated and excreted. Most of the unconjugated is recirculated through the enterohepatic circulation.
    • Unconjugated hyperbilirubinemia is the predominant form of physiological jaundice.
    • Physiologic jaundice is a benign case and resolves within a 10 to 14 days of life.
  • Pathological jaundice: [13]
    • The majority of neonatal jaundice is due to pathological conditions. Pathological neonatal jaundice is due to acquired or inherited conditions.
    • Pathological jaundice is the result of an increase in the level of unconjugated bilirubin which is named as "Indirect hyperbilirubinemia".
    • It includes some features like the appearance of jaundice within the first day of life, persistent jaundice manifestations more than two weeks, and dark urine.
    • Acquired pathological neonatal jaundice develops mainly due to hemolysis of the red blood cells via three main diseases:[14]
      • Rhesus (Rh) hemolytic disease
      • ABO blood group incompatibility
      • Glucose 6 phosphate dehydrogenase enzyme deficiency (G6PD deficiency)
    • Inhereted pathological neonatal jaundice occurs due to a defect in the bilirubin metabolism process and it includes the following:[15]
      • Defective hepatic uptake and storage of the bilirubin
      • Defective bilirubin conjugation to glucuronic acid and it includes the following syndromes:
        • Gilbert syndrome
        • Crigler-Najjar syndrome
        • Lucey-Driscoll syndrome
        • Breast milk jaundice
      • Defective excretion of bilirubin into the bile and this syndrome called Dubin-Johnson syndrome
      • Defective reuptake of the conjugated bilirubin through the enterohepatic ciruclation. This syndrome called Rottor syndrome.

Acquired pathological neonatal jaundice

  • The following table contains the different hemolytic mechanisms which lead to neonatal jaundice:[16][17]
Hemolytic disease Pathogenesis
Rhesus factor (Rh) hemolytic disease
  • It is known as the Rh hemolytic disease of the newborns (RHDN).
  • RHDN is the result of alloimmunization of the maternal red blood cells when the mother is pregnant with a Rh-positive fetus.
  • In the first pregnancy, if the fetus is a Rh-positive, some of the fetal blood is mixed with the maternal blood during birth. The maternal body will form antibodies (IgG) against the fetal Rh antigen and the first birth is not affected.
  • In the second birth, if the fetus is a Rh-positive, the formed maternal anti-Rh antibodies will cause hemolysis to the fetal blood. This condition may be mild or severe hemolytic anemia and may end up with hydrops fetalis.
ABO blood group incompatibility
  • ABO blood group incompatibility is another form of the alloimmunization of the maternal blood cells against the fetal erythrocytes.
  • ABO incompatibility occurs when the mother has O group of the blood and pregnant in a fetus with A or B blood group.
  • The maternal blood cells will form eitantibodieA antibodies or anti-B antibodies (IgM) which can cross the placenta and causes hemolysis of the fetal erythrocytes causing increase the unconjugated bilirubin and jaundice.
  • This condition, unlike RHDN, develops in the first newborn.
G6PD deficiency
  • G6PD is an important enzyme found in the red blood cells and incorporated in the hexose monophosphate pathway. G6PD collaborates in the production of NADPH and reduction of glutathione thus, helping in decrease the oxidative stress around the RBCs.
  • A deficiency in the G6PD occurs due to a genetic defect which will lead to increas the oxidative stress on the RBCs and the hemolysis of the fetal blood cells.

Inherited pathological neonatal jaundice

  • The following table includes the different causes of inherited neonatal jaundice:
Defective mechanism Pathogenesis
Defective bilirubin hepatic reuptake and storage[18]
  • Defective of bilirubin hepatic uptake and storage is not well understood. The recently held studies revealed the correlation between mutations in the GST gene and neonatal jaundice.
  • The gene deletion in GST-M gene class is believed it leads to dysfunction of the GSTM1 enzyme and defective hepatic uptake of bilirubin
Disorder of bilirubin conjugation Gilbert syndrome:[19]
  • Gilbert syndrome, the most common inherited neonatal jaundice syndrome, is an autosomal recessive disease which is one of the causes of neonatal jaundice due to a defect (not total absence) in the Uridine diphosphate Glucuronsyl Transferase (UGT) enzyme.
  • It is accompanied by several gene mutations (about 100 different mutations).
  • The most common gene mutation occurs in the TA sequence of the TATAA box of the promoter region of UGT1A1 gene.
Crigler-Najjar syndrome type I:[20][21]
  • Crigler Najjar syndrome type I is characterized by a total absence of the UGT1A1 enzyme, unlike Gilbert syndrome.
  • Gene mutation of the UGT1A1 enzyme occurs due to deletion of the amino acid sequences of the exons of the UGT1A1 enzyme.
  • Genetic mutations in the introns also can lead to frameshift of the amino acid sequences or create premature stop codons which result in cessation of the enzyme formation.
Crigler-Najjar syndrome type II (Arias syndrome):[22]
  • Crigler Najjar syndrome type II has a reduced activity of the UGT1A1 enzyme (not completely inactive).
  • The gene mutation in the UGT1A1 gene is point mutation which results in amino acid substitution not stop codon. Hereby, a decrease in the UGT enzyme occurs.
Lucey-Driscoll syndrome:[23]
  • Also known as the transient familial neonatal hyperbilirubinemia as it is a rare familial disease which results in severe hyperbilirubinemia in the first 24 hours of life.
  • It is believed that Lucey-Driscoll syndrome is associated with an inhibitor of the UGT1A1 enzyme and this inhibitor is unidentified until the moment.
Breast milk jaundice:[24]
  • Breast milk jaundice is one of the benign causes of neonatal jaundice with no specific pathogenesis process. It is considered as the continuation of physiologic jaundice beyond one week. l
  • It is believed that a combination of genetic mutation and environmental (breast milk components) factors lead to the jaundice development.
  • The beta-glucuronidase enzyme, one of the milk substances, may be one of the causes that increase the bilirubin and develop jaundice.
  • In a Japanese study, a correlation between a genetic mutation in UGT1A1 gene and breast milk jaundice has been considered.
Disorders of excretion into Bile Dubin-Johnson syndrome:[25]
  •  Dubin-Johnson syndrome is a result of a genetic mutation in the ABCC2/MRP2 transporter result in absence of the transporter expression.
  • Other mutations which may lead to Dubin-Johnson syndrome include base deletion, nonsense mutation, or exon skipping.
Disorders of reuptake Rotor syndrome (RS):[26]
  • Rotor syndrome is an autosomal recessive disease which results in a defect of the hepatic reuptake of the bilirubin.
  • Genetic mutation of SLCO1B1/OATP1B1 andSLCO1B3/OATP1B3 lead to absence of the OATP1B1 and OATP1B3 transporters of bilirubin.

References

  1. ↑ Berk PD, Howe RB, Bloomer JR, Berlin NI (1969). "Studies of bilirubin kinetics in normal adults". J Clin Invest. 48 (11): 2176–90. doi:10.1172/JCI106184. PMC 297471. PMID 5824077.
  2. ↑ LONDON IM, WEST R, SHEMIN D, RITTENBERG D (1950). "On the origin of bile pigment in normal man". J Biol Chem. 184 (1): 351–8. PMID 15422003.
  3. ↑ Knobloch E, Hodr R, Herzmann J, Houdková V (1986). "Kinetics of the formation of biliverdin during the photochemical oxidation of bilirubin monitored by column liquid chromatography". J Chromatogr. 375 (2): 245–53. PMID 3700551.
  4. ↑ Bissell DM, Hammaker L, Schmid R (1972). "Liver sinusoidal cells. Identification of a subpopulation for erythrocyte catabolism". J Cell Biol. 54 (1): 107–19. PMC 2108858. PMID 5038868.
  5. ↑ Paludetto R, Mansi G, Raimondi F, Romano A, Crivaro V, Bussi M; et al. (2002). "Moderate hyperbilirubinemia induces a transient alteration of neonatal behavior". Pediatrics. 110 (4): e50. PMID 12359823.
  6. ↑ Weiss JS, Gautam A, Lauff JJ, Sundberg MW, Jatlow P, Boyer JL; et al. (1983). "The clinical importance of a protein-bound fraction of serum bilirubin in patients with hyperbilirubinemia". N Engl J Med. 309 (3): 147–50. doi:10.1056/NEJM198307213090305. PMID 6866015.
  7. ↑ Chowdhury JR, Chowdhury NR, Wu G, Shouval R, Arias IM (1981). "Bilirubin mono- and diglucuronide formation by human liver in vitro: assay by high-pressure liquid chromatography". Hepatology. 1 (6): 622–7. PMID 6796486.
  8. ↑ Bosma PJ, Seppen J, Goldhoorn B, Bakker C, Oude Elferink RP, Chowdhury JR; et al. (1994). "Bilirubin UDP-glucuronosyltransferase 1 is the only relevant bilirubin glucuronidating isoform in man". J Biol Chem. 269 (27): 17960–4. PMID 8027054.
  9. ↑ Vítek L, Zelenka J, Zadinová M, Malina J (2005). "The impact of intestinal microflora on serum bilirubin levels". J Hepatol. 42 (2): 238–43. doi:10.1016/j.jhep.2004.10.012. PMID 15664250.
  10. ↑ Ullah S, Rahman K, Hedayati M (2016). "Hyperbilirubinemia in Neonates: Types, Causes, Clinical Examinations, Preventive Measures and Treatments: A Narrative Review Article". Iran J Public Health. 45 (5): 558–68. PMC 4935699. PMID 27398328.
  11. ↑ Dennery PA, Seidman DS, Stevenson DK (2001). "Neonatal hyperbilirubinemia". N Engl J Med. 344 (8): 581–90. doi:10.1056/NEJM200102223440807. PMID 11207355.
  12. ↑ Brouillard RP (1974). "Measurement of red blood cell life-span". JAMA. 230 (9): 1304–5. PMID 4479604.
  13. ↑ Ullah S, Rahman K, Hedayati M (2016). "Hyperbilirubinemia in Neonates: Types, Causes, Clinical Examinations, Preventive Measures and Treatments: A Narrative Review Article". Iran J Public Health. 45 (5): 558–68. PMC 4935699. PMID 27398328.
  14. ↑ Watchko JF, Lin Z, Clark RH, Kelleher AS, Walker MW, Spitzer AR; et al. (2009). "Complex multifactorial nature of significant hyperbilirubinemia in neonates". Pediatrics. 124 (5): e868–77. doi:10.1542/peds.2009-0460. PMID 19858149.
  15. ↑ Memon N, Weinberger BI, Hegyi T, Aleksunes LM (2016). "Inherited disorders of bilirubin clearance". Pediatr Res. 79 (3): 378–86. doi:10.1038/pr.2015.247. PMC 4821713. PMID 26595536.
  16. ↑ McDonnell M, Hannam S, Devane SP (1998). "Hydrops fetalis due to ABO incompatibility". Arch Dis Child Fetal Neonatal Ed. 78 (3): F220–1. PMC 1720779. PMID 9713036.
  17. ↑ Kaplan M, Hammerman C (2004). "Glucose-6-phosphate dehydrogenase deficiency: a hidden risk for kernicterus". Semin Perinatol. 28 (5): 356–64. PMID 15686267.
  18. ↑ Muslu N, Dogruer ZN, Eskandari G, Atici A, Kul S, Atik U (2008). "Are glutathione S-transferase gene polymorphisms linked to neonatal jaundice?". Eur J Pediatr. 167 (1): 57–61. doi:10.1007/s00431-007-0425-z. PMID 17318621.
  19. ↑ Bosma PJ, Chowdhury JR, Bakker C, Gantla S, de Boer A, Oostra BA; et al. (1995). "The genetic basis of the reduced expression of bilirubin UDP-glucuronosyltransferase 1 in Gilbert's syndrome". N Engl J Med. 333 (18): 1171–5. doi:10.1056/NEJM199511023331802. PMID 7565971.
  20. ↑ Gantla S, Bakker CT, Deocharan B, Thummala NR, Zweiner J, Sinaasappel M; et al. (1998). "Splice-site mutations: a novel genetic mechanism of Crigler-Najjar syndrome type 1". Am J Hum Genet. 62 (3): 585–92. doi:10.1086/301756. PMC 1376950. PMID 9497253.
  21. ↑ Canu G, Minucci A, Zuppi C, Capoluongo E (2013). "Gilbert and Crigler Najjar syndromes: an update of the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene mutation database". Blood Cells Mol Dis. 50 (4): 273–80. doi:10.1016/j.bcmd.2013.01.003. PMID 23403257.
  22. ↑ Seppen J, Bosma PJ, Goldhoorn BG, Bakker CT, Chowdhury JR, Chowdhury NR; et al. (1994). "Discrimination between Crigler-Najjar type I and II by expression of mutant bilirubin uridine diphosphate-glucuronosyltransferase". J Clin Invest. 94 (6): 2385–91. doi:10.1172/JCI117604. PMC 330068. PMID 7989595.
  23. ↑ ARIAS IM, WOLFSON S, LUCEY JF, MCKAY RJ (1965). "TRANSIENT FAMILIAL NEONATAL HYPERBILIRUBINEMIA". J Clin Invest. 44: 1442–50. doi:10.1172/JCI105250. PMC 292625. PMID 14332157.
  24. ↑ Gourley GR, Arend RA (1986). "beta-Glucuronidase and hyperbilirubinaemia in breast-fed and formula-fed babies". Lancet. 1 (8482): 644–6. PMID 2869347.
  25. ↑ Paulusma CC, Kool M, Bosma PJ, Scheffer GL, ter Borg F, Scheper RJ; et al. (1997). "A mutation in the human canalicular multispecific organic anion transporter gene causes the Dubin-Johnson syndrome". Hepatology. 25 (6): 1539–42. doi:10.1002/hep.510250635. PMID 9185779.
  26. ↑ van de Steeg E, Stránecký V, Hartmannová H, Nosková L, Hřebíček M, Wagenaar E; et al. (2012). "Complete OATP1B1 and OATP1B3 deficiency causes human Rotor syndrome by interrupting conjugated bilirubin reuptake into the liver". J Clin Invest. 122 (2): 519–28. doi:10.1172/JCI59526. PMC 3266790. PMID 22232210.


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