Icterus

The primary cause of jaundice is the accumulation of excess bilirubin, which gets deposited in the skin and mucous membranes. Jaundice becomes clinically noticeable only when bilirubin levels exceed 3 mg/L. The two main types of hemolysis that lead to hyperbilirubinemia and jaundice are intravascular and extravascular hemolysis.

Intravascular hemolysis occurs when red blood cells are destroyed within the bloodstream. This can result from mechanical damage to the endothelium, autoimmune processes involving complement and antibodies, infections (such as malaria), oxidative stress (due to low G6PD levels), or physical shearing from a malfunctioning aortic valve or fibrin strands in small vessels (as seen in microangiopathic anemias).

Extravascular hemolysis, which is more prevalent, involves the removal and destruction of red blood cells by macrophages in the spleen or liver, as seen in conditions like hereditary spherocytosis or sickle cell anemia.

It’s important to note that certain conditions, such as G6PD deficiency and immunologically mediated hemolytic anemia, may exhibit characteristics of both intravascular and extravascular destruction. The mechanism for the removal of cells from circulation is determined by the specific pathophysiology of the disorder.

Causes

Icterus can arise from various factors, including:

1. Pre-Hepatic Causes: Conditions that lead to increased bilirubin production, such as hemolytic anemia, where red blood cells are destroyed faster than they can be produced.
2. Hepatic Causes: Liver diseases that impair bilirubin processing, including:
   • Hepatitis (viral, alcoholic, autoimmune)
   • Cirrhosis
   • Liver tumors
3. Post-Hepatic Causes: Conditions that obstruct bile flow, leading to increased bilirubin levels, such as:
   • Gallstones
   • Pancreatic cancer
   • Biliary strictures

Differential Diagnoses

When evaluating icterus, it is important to consider other conditions that may present similarly. Differential diagnoses include:

1. Cholestasis: A condition where bile flow is impaired, leading to jaundice and pruritus (itching).
2. Gilbert’s Syndrome: A benign genetic condition characterized by intermittent mild jaundice due to reduced bilirubin conjugation.
3. Crigler-Najjar Syndrome: A rare genetic disorder affecting bilirubin metabolism, leading to severe jaundice.
4. Hemolytic Anemia: Conditions such as sickle cell disease or thalassemia can cause increased bilirubin due to rapid red blood cell destruction.
5. Liver Disease: Various liver conditions can lead to jaundice, including hepatitis, cirrhosis, and liver cancer.