PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML): A REVIEW FOR PG PREPARATION

Posted: August 15, 2015 in Repeated Topics In PG Entrance
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PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML)

  • Cause: A progressive disease caused by JC virus

 

  • Affected cells: Oligodendrocytes

 

Pathology:

Since oligodendrocytes are concerned with myelination; PML is associated with multifocal areas of demyelination distributed throughout the brain but sparing spinal cord and optic nerve.

 

Cellular changes:

  • Oligodendrocytes: Densely staining enlarged nuclei containing viral inclusions
  • Astrocytes: Hyperchromatic, deformed, bizarre nuclei containing mitotic figures.

 

Associated conditions:

PML is predominantly seen in patients with immunosuppressive disorders: AIDS (80%), hematological malignancies, transplant recipients.

 

Symptoms:

  • Focal neurological signs: Aphasia, dysarthria, hemiparesis/ monoparesis, ataxia
  • Visual impairment (45%): Homonymous hemianopia
  • Mental impairment (38%): Behavioral change, confusion, dementia
  • Seizures (20%).

 

Diagnosis:

  • MRI is the investigation of choice for PML as it is superior than CT and shows classical asymmetric nonenhancing coalescing lesions in white matter located periventricularly.
  • PCR amplification of JCV-DNA in association with typical MRI lesion is diagnostic of PML.
  • Brain biopsy demonstrates multiple demyelinating lesion in white matter of cerebrum, cerebellum and brainstem.

 

Prognosis:

In most cases, death occurs within 3-6 months from the onset of neurological symptoms and even more rapidly in patients with AIDS.

 

Treatment:

  • Currently, the best available therapy is reversal of the immune-deficient state, since there are no effective drugs that block virus infection without toxicity.
  • In the case of HIV-associated PML, immediately beginning ART will benefit most individuals.
  • Drugs that are being studies as potential treatment options (still not recommended): Cidofovir and Mefloquine.
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