II. Risk Factors: Immunosuppression

  1. AIDS Defining Illness (CD4 <200/mm3)
  2. Chemotherapy for Lymphoma
  3. Immunosuppressants post-organ transplant
  4. Multiple Sclerosis medications
  5. Rheumatoid Arthritis medications
  6. Systemic Lupus Erythematosus medications

III. Pathophysiology

  1. JC Virus infection (Polyomavirus JC) is common organism present without consequence in most patients
  2. Suppressed Immunity allows for Encephalitis

IV. Signs

  1. Cognitive Decline
  2. Cranial Nerve Palsy
  3. Aphasia
  4. Ataxia
  5. Weakness
  6. Sensory loss
  7. Seizure

V. Imaging: MRI Brain

  1. Single or multiple white matter lesions
  2. Minimal to no enhancement, edema, or mass effect

VI. Diagnosis

  1. JC Virus PCR detection from CSF
  2. Brain Biopsy (rarely done)

VII. Management

  1. Reverse immune deficiency

VIII. Prognosis

  1. Mortality: 30-50% over months following onset
  2. Morbidity: Debilitating residual cognitive deficits are common in those who survive

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