Introduction:
Jaundice (from the French word Jaune, meaning yellow) is a clinical condition marked by the yellow discoloration of the skin and the white part of the eyes (sclera). It occurs due to elevated levels of bilirubin in the blood — a condition medically referred to as hyperbilirubinemia.
Under normal conditions, the serum bilirubin level ranges from 0.2 to 1.0 mg/dL, with 0.2–0.6 mg/dL being unconjugated bilirubin and 0.2–0.4 mg/dL being conjugated bilirubin. When bilirubin levels rise, it accumulates in tissues, causing the yellowish pigmentation characteristic of jaundice.
Classification of Jaundice
Jaundice is not a disease by itself but a symptom of an underlying disorder. It can occur due to multiple causes and is broadly classified into three types for better understanding:
- 1) Hemolytic Jaundice
- 2) Hepatic (Hepatocellular) Jaundice
- 3) Obstructive (Regurgitation) Jaundice
1) Hemolytic Jaundice
This type of jaundice occurs due to excessive breakdown (hemolysis) of red blood cells, leading to overproduction of unconjugated bilirubin. The liver’s capacity to conjugate bilirubin becomes overwhelmed, even though it normally handles up to 3 g of bilirubin daily compared to the usual production of 0.3 g.
Causes: Incompatible blood transfusion, malaria, sickle-cell anemia, and other hemolytic conditions.
Biochemical Features:
- Elevation of unconjugated bilirubin in serum
- Increased excretion of urobilinogen in urine
- Dark brown stools due to excess stercobilinogen
2) Hepatic (Hepatocellular) Jaundice
Hepatic jaundice results from damage to the liver cells (hepatocytes) that impairs the uptake, conjugation, and excretion of bilirubin. It can be caused by viral hepatitis, toxic injury (from chloroform, carbon tetrachloride, or phosphorus), liver cirrhosis, or cardiac failure.
Biochemical Features:
- Elevation of both conjugated and unconjugated bilirubin in serum
- Dark urine due to bilirubin and urobilinogen excretion
- Increased liver enzymes — ALT (SGPT) and AST (SGOT)
- Pale clay-colored stools due to lack of stercobilinogen
- Symptoms include nausea, loss of appetite (anorexia), and fatigue
3) Obstructive (Regurgitation) Jaundice
This type of jaundice is caused by an obstruction in the bile duct, preventing bile flow into the intestine. Common causes include gallstones and tumors.
Biochemical Features:
- Increased conjugated bilirubin in serum
- Elevated alkaline phosphatase due to bile duct damage
- Dark urine from bilirubin excretion
- Clay-colored stools due to lack of stercobilinogen
- Fatty stools (steatorrhea) due to impaired fat digestion
- Nausea and abdominal pain
Jaundice Due to Genetic Defects
Some hereditary or congenital conditions can cause jaundice due to enzyme deficiencies involved in bilirubin metabolism.
1) Neonatal (Physiological) Jaundice
This is not a true genetic defect but results from increased red blood cell breakdown and immature liver function in newborns. The enzyme UDP-glucuronyl transferase, responsible for bilirubin conjugation, is less active, and substrate (UDP-glucuronic acid) levels are low.
Consequences: Excess unconjugated bilirubin (sometimes above 25 mg/dL) can cross the blood-brain barrier, leading to kernicterus (bilirubin-induced brain damage), causing neurological defects or mental retardation.
Treatment:
- Phenobarbital: Induces bilirubin-metabolizing enzymes.
- Phototherapy: Exposing the infant to blue light (420–470 nm) converts bilirubin into a harmless water-soluble form called lumirubin, which is easily excreted.
- In severe cases, blood transfusion may be required to prevent brain damage.
2) Crigler–Najjar Syndrome Type I
This rare congenital disorder results from complete absence of UDP-glucuronyl transferase. Bilirubin conjugation cannot occur, leading to very high serum unconjugated bilirubin levels. Most affected infants die within the first two years of life due to severe jaundice and brain damage.
3) Crigler–Najjar Syndrome Type II
A milder hereditary defect in bilirubin conjugation caused by partial deficiency of UDP-glucuronyl transferase. The enzyme responsible for adding the second glucuronyl group is defective. Serum bilirubin levels remain below 20 mg/dL and are less life-threatening than Type I.
4) Gilbert’s Disease
Gilbert’s syndrome is a common, mild hereditary condition caused by multiple minor defects:
- Reduced hepatic uptake of bilirubin
- Decreased activity of UDP-glucuronyl transferase
- Slower clearance of bilirubin from the liver
Patients typically have mild, fluctuating jaundice that may become noticeable during stress, fasting, or illness.
Detailed Notes:
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