Hepatitis A through E Lecture Notes

Introduction

• Discussion on hepatitis viruses A through E
• Topics covered: Epidemiology, Etiology, Virology, Clinical manifestations, Serology

Key Points to Remember

1. Route of Transmission
2. Acute or Chronic Infection
3. Virus Structure

Hepatitis A (HAV)

• Infection Type: Acute infection
  • Cleared from the body typically in less than six months
• Route of Transmission: Fecal-oral contamination
  • Mnemonic: "A for Anus"
• Virus Structure:
  • Non-enveloped virus
  • Single-stranded RNA (Positive-sense)

Hepatitis B (HBV)

• Infection Type: Acute and Chronic infection
• Route of Transmission:
  1. Sexual
  2. Blood (needles, transfusions)
  3. Perinatal (mother to child)
• Virus Structure:
  • Enveloped virus
  • Partially double-stranded DNA

Hepatitis C (HCV)

• Infection Type: Acute and Chronic infection
• Route of Transmission: Same as HBV:
  1. Sexual
  2. Blood
  3. Perinatal
• Virus Structure:
  • Enveloped virus
  • Single-stranded RNA (Positive-sense)

Hepatitis D (HDV)

• Infection Type: Mainly Chronic infection
• Route of Transmission: Same as HBV and HCV
• Requires HBV for infection:
  • Co-infection (simultaneous infection)
  • Superinfection (HDV infects already HBV-infected cell)
• Virus Structure:
  • Enveloped virus
  • Circular single-stranded RNA (Negative-sense)

Hepatitis E (HEV)

• Infection Type: Mainly Acute infection
  • Chronic only in immunocompromised patients
• Route of Transmission: Fecal-oral (same as HAV)
  • Mnemonic: "E for Eat"
• Virus Structure:
  • Non-enveloped virus
  • Single-stranded RNA (Positive-sense)

Pathophysiology of Hepatitis Viruses

Infection Mechanism

• Entry into Hepatocytes: Through endocytosis
• Viral Replication:
  • RNA viruses use host's ribosomes to synthesize proteins
  • HBV releases partial double-stranded DNA which gets completed by host enzymes
• Cell Damage: Leads to hepatocyte lysis, inflammation, and immune response

Immune Response

• Cytotoxic T cells recognize infected cells through MHC-1
• T cells release perforins and granzymes inducing apoptosis of infected hepatocytes

Clinical Manifestations

Initial Phase (Prodromal Phase)

• Symptoms: Fever, malaise, nausea, vomiting, weight loss, diarrhea

Second Phase (Icteric Phase)

• Symptoms:
  • Jaundice (yellow sclera and skin)
  • Dark urine
  • Pale stools (acolytic)
  • Hepatomegaly
  • Right upper quadrant pain

Third Phase (Convalescent Phase)

• Resolution of symptoms
• Liver enzymes start to normalize

Lab Findings

• Increased bilirubin levels (conjugated and unconjugated)
• Elevated liver enzymes (AST, ALT, alkaline phosphatase)
• Prolonged PT and PTT due to decreased clotting factors

Extrahepatic Manifestations

• More common with HBV and HCV:
  • Arthritis, vasculitis, glomerulonephritis, myocarditis
• Thrombocytopenia and hemolytic anemia due to immune complexes

Chronic Infection Concerns

• Risk of fibrosis and cirrhosis from ongoing damage
• Increased risk of hepatocellular carcinoma due to dysplasia from excessive mitosis

Conclusion

• Overview of hepatitis viruses A to E
• Understanding of their transmission, structure, and pathophysiological effects

Additional Resources

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