Pelizaeus Merzbacher Disease

Pelizaeus-Merzbacher disease, an X-linked recessive disorder, is caused by mutations in a gene on chromosome xg22 encoding myelin proteolipid protein. A deficiency of myelin proteolipid protein accounts for the defective myelination.

The disease presents in two forms: connatal and childhood. The connatal form manifests with psycho-motor retardation, optic atrophy, and nystagmus. Death usually occurs by 2 years of age. The childhood form, presenting with spasticity, cerebellar symptoms, and optic atrophy, has a slower clinical course, extending into adulthood.

Grossly, the brain is atrophic. Histologically, the white matter in the brain and spinal cord shows failure of myelination, hypomyelination, and perivascu-lar myelin islands, giving the characteristic tigroid appearance. The density of nerve fibers is relatively normal. The number of oligodendrocytes is variably reduced.

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