Hepatitis Overview and Causes

Hepatitis Overview

• Hepatitis is inflammation of the liver, which can be acute or chronic.
• It can result from viral infections (Hepatitis A, B, C, D, and E), alcohol abuse, toxins, autoimmune disorders, and certain medications.

Most Likely Causes

• Viral Hepatitis
  • Hepatitis A: Caused by Hepatitis A virus (HAV).
  • Hepatitis B: Caused by Hepatitis B virus (HBV).
  • Hepatitis C: Caused by Hepatitis C virus (HCV).
  • Hepatitis D: Caused by Hepatitis D virus (HDV) only infects people already infected with HBV.
  • Hepatitis E: Caused by Hepatitis E virus (HEV).
• Non-viral Hepatitis
  • Alcohol-induced hepatitis: Caused by acetaldehyde (alcohol metabolite).
  • Drug-induced hepatitis: Caused by hepatotoxic medications (acetaminophen, NSAIDs, antibiotics).
  • Autoimmune hepatitis: Immune system attacks hepatocytes (liver cells), often with antinuclear antibodies (ANA) and anti-smooth muscle antibodies (ASMA).
  • Non-alcoholic steatohepatitis (NASH): Fat accumulation in hepatocytes due to metabolic dysfunction, often seen in obesity, diabetes, and metabolic syndrome.

Pathophysiology

• Infection/Exposure:
  • Viral hepatitis: Viruses infect hepatocytes, triggering an immune response.
  • Alcoholic hepatitis: Acetaldehyde disrupts hepatocytes, promoting oxidative stress and inflammation.
  • Autoimmune hepatitis: T cells attack hepatocytes, leading to immune-mediated destruction.
• Inflammatory Response:
  • Immune system targets infected/damaged hepatocytes, leading to recruitment of macrophages, cytokines, and natural killer (NK) cells.
  • This process leads to hepatocyte necrosis, liver enzyme release (AST, ALT), and fibrosis (scar tissue).

Liver Damage and Scarring

• Persistent inflammation leads to fibrosis, impairing blood flow and bile excretion.
• Ongoing fibrosis can progress to cirrhosis, altering liver architecture and causing portal hypertension.
• Cirrhosis increases the risk of hepatocellular carcinoma (HCC).

Chronic Hepatitis

• Chronic hepatitis (e.g., Hepatitis B, C, D) can persist due to the immune system's inability to eliminate the virus, leading to ongoing inflammation, fibrosis, and a higher risk of cirrhosis and liver cancer.

Disease Transmission

• Hepatitis A: Fecal-oral through contaminated food, water, or close contact.
• Hepatitis B: Contact with infected blood, bodily fluids (semen, vaginal fluid), sexual contact, and vertical transmission.
• Hepatitis C: Contact with infected blood, often through needle sharing, blood transfusions, and contaminated medical equipment.
• Hepatitis D: Only infects individuals already infected with HBV, transmitted the same ways as HBV.
• Hepatitis E: Fecal-oral, similar to Hepatitis A but more dangerous in pregnant women.
• Non-viral Hepatitis: Not infectious, occurring due to toxins, alcohol, or autoimmune processes.

Risk Factors

• Viral Hepatitis: Travel to endemic areas (poor sanitation), contaminated food/water, unprotected sex, needles sharing, healthcare exposure, vertical transmission, etc.
• Alcoholic Hepatitis: Chronic alcohol consumption.
• Drug-induced Hepatitis: Use of hepatotoxic drugs.
• Autoimmune Hepatitis: Presence of autoimmune diseases.
• NASH: Obesity, Type 2 diabetes, metabolic syndrome, poor diet.