Pelizaeus–Merzbacher disease

Pelizaeus–Merzbacher disease is a rare inherited leukodystrophy, usually caused by PLP1 variants, that disrupts myelin formation in the central nervous system and impairs neurological function.

PLP1: PLP1 is a gene encoding proteolipid protein 1, a major structural protein of central nervous system myelin. Most cases arise from PLP1 changes that alter myelin production or the cells that produce it.
Classic Pelizaeus–Merzbacher disease: Classic Pelizaeus–Merzbacher disease is a severe early-onset form with nystagmus, hypotonia, and delayed motor development. It illustrates the characteristic infantile presentation of the disease.
Leukodystrophy: A leukodystrophy is an inherited disorder that primarily affects the brain’s white matter. Pelizaeus–Merzbacher disease belongs to this broad group of white-matter disorders.
Magnetic resonance imaging: Magnetic resonance imaging is a medical imaging technique that uses magnetic fields and radio waves to produce internal body images. Brain MRI can reveal diffuse white-matter abnormalities and support recognition of hypomyelination.
Proteolipid protein 1: Proteolipid protein 1 is a membrane protein abundant in myelin made by oligodendrocytes. This protein is the principal product of the gene most often implicated in the disease.
Connatal Pelizaeus–Merzbacher disease: Connatal Pelizaeus–Merzbacher disease is the most severe form, with symptoms evident at or soon after birth. This form marks the severe end of the disease’s clinical range.
Hypomyelinating leukodystrophy: A hypomyelinating leukodystrophy is an inherited disorder marked by persistently inadequate myelin formation. This category captures the central tissue pattern shared by the disease.
Genetic testing: Genetic testing analyzes DNA to identify variants associated with inherited conditions. Testing PLP1 can confirm the molecular diagnosis and clarify inheritance.
Oligodendrocyte: An oligodendrocyte is a central nervous system cell that forms and maintains myelin around axons. PLP1-related cellular stress disrupts the cells responsible for making myelin.
SPG2: SPG2 is a spectrum of X-linked spastic paraplegia phenotypes associated with PLP1 variants. Some PLP1 variants cause predominantly spastic paraplegia rather than classic leukodystrophy.

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Canavan diseaseCompared with: Both impair myelin, but Pelizaeus–Merzbacher disease is usually a hypomyelination disorder rather than N-acetylaspartic acid accumulation.