Pelizaeus-Merzbacher Disease (PMD)



X-linked Inheritance Inherited through the X chromosome

Age range at onset:

Neonatal or Infancy

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Usually, symptoms of Pelizaeus-Merzbacher disease appear in the first year of life with abnormal eye movements (nystagmus) or noisy breathing (stridor) often being present in the first month of life. Development is slow and abnormal motor development with stiffness, ataxia and abnormal movements develop. Epileptic seizures are common. Poor vision develops in many people.

Learning difficulties are common but is relatively less affected than the movement problems. Curvature of the spine (kyphoscoliosis) is common.

Development may slowly improve up to the age of 10 or 12 years but afterwards there is a very slow decline in physical and cognitive abilities with most people not living beyond mid adult years.


Pelizaeus-Merzbacher disease (PMD) is caused by mutations in the proteolipid protein gene (PLP1) which is on the X chromosome. This gene is responsible for the production of proteolipid protein which is one of the major components of myelin in the brain.

Mothers of boys with classical PMD may sometimes have symptoms such as walking difficulties, bladder problems or cognitive difficulties.

Mutations in the PLP1 gene sometimes cause progressive stiffness in the legs only (spastic paraparesis) without involvement of the brain.


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