PELIZAEUS-MERZBACHER DISEASE
 
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PELIZAEUS-MERZBACHER DISEASE

 

DEFINITION:

A neurodegenerative disorder characterized by degeneration of central nervous system (CNS) white matter and specific CNS pathological findings.

EPIDEMIOLOGY:

  • incidence: rare
  • age of onset:
    • newborn to adulthood (depends on the Form)
  • risk factors:
    • familial
      • Types I: X-linked recessive (Xq22), also autosomal recessive and sporadic forms
      • Type II: X-linked recessive, also autosomal dominant
      • Type III: sporadic
      • Type IV: autosomal dominant (AD)

PATHOGENESIS:

1. Background

  • a genetic defect (i.e., at Xq22) -> impaired biosynthesis of a proteolipid apoprotein -> impaired differentiation and maintenance of oligodendrocytes -> loss of myelin within intact axons

PATHOLOGY:

1. Trigoid Appearance

  • patchy areas of demyelination with preservation of perivascular islands throughout the cerebral and cerebellar hemispheres

2. Others

  • positive staining with sudan (sudanophilic) identifies areas of myelin breakdown
  • decreased number of oligodendrocytes
  • normal nerve cells and axons

TYPES:

  • TYPE I: Classic
  • TYPE II: Connatal Form
  • TYPE III: Transitional Form
  • TYPE IV: Adult Form
  • TYPE V: Variant Form
  • TYPE VI: Cockayne's Syndrome

    • CLINICAL FEATURES:

    1. Type I - Classical Variant

    • infantile onset - onset within the 1st few months of life
    • most are male
    • death in the 2nd or 3rd decades

      1. Neurological Manifestations

    • 1. Initial
      • spasmus nutans:
      • pendular nystagmus and roving eye movements
      • head nodding, tilt, and tremor
    • 2. Later
      • delayed psychomotor development
      • movement disorders
      • ataxia, chorea, choreoathetosis, spasticity, intention tremor
      • others
      • dysarthria, mild dementia, optic atrophy, seizures

    2. Type II - Connatal Form

    • neonatal onset - onset within the neonatal period
    • initial and later findings similar to the classical variant only develop more rapidly with death by 5-7 years of age

    3. Type III - Transitional Form

    • onset soon after the neonatal period
    • phenotypically lies between Types I and II with death between
    • 5-10 years of age

    INVESTIGATIONS:

    1. Imaging Studies

    1. CT/MRI

    • progressive leukodystrophy
    • diffuse or patchy demyelination of hemispheres with persistent islands of myelin
    • cerebral and cerebellar atrophy with dilated ventricles seen in the latter stage

    2. Others

    1. Brainstem Auditory Evoked Potential

    • loss of waves III-V

    MANAGEMENT:

    1. Supportive

    • no treatment available to reverse the demyelination
    • treat movement disorders and seizures

     

     

     

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