Review Note

Slow Infections

• Infections causing long-lasting, slowly progressing diseases.
• Characterized by a very long incubation period (up to months or years).
• Most commonly manifest in the CNS with multiple neurological symptoms.
• No cure available; they ultimately lead to the death of the patient.
• Types:
  • Prion diseases or slow viral infections.
    
    

• Causative Agent:
  • Prions (misfolded proteins).
  • Diseases include:
    • Creutzfeldt-Jakob Disease (CJD) – most common.
    • Kuru.
    • Fatal familial insomnia.

• Examples:
  • JC virus → Progressive multifocal leukoencephalopathy (PML).
  • Measles → Subacute sclerosing panencephalitis (SSPE).
  • Rubella → Progressive rubella panencephalitis (PRP).

Characterization of Prions:

• Prions are misfolded proteins; they lack RNA or DNA.
• Accumulate in brain tissue, causing spongiform degeneration (replacement of healthy tissue with fluid-filled cysts, giving the brain a sponge-like appearance).
• Prion diseases are collectively termed transmissible spongiform encephalopathies (TSE).
• Extremely rare diseases caused by:
  • Hereditary syndromes.
  • Sporadic occurrence.
  • Ingestion of contaminated food.
  • Contaminated organ transplants.
• Characterized by a very long incubation period.
• No cure; lead to death within months to years.

Key Facts:

• Cause of Death:
  • Aspiration pneumonia is the most common cause of death in TSE.
• Diagnosis:
  • Confirmed by brain biopsy or during autopsy.
    
    

General Symptoms of Prion Diseases:

• Rapidly developing dementia.
• Neurological symptoms:
  • Myoclonic jerks.
  • Gait changes.
  • Ataxia.
  • Seizures.
• Hallucinations.
• Muscle stiffness.
• Confusion.
• Fatigue.
• Speech difficulties.
• Pathological laughter (notably seen in Kuru).