Pelizaeus Merzbacher disease (PMD)

What is Pelizaeus Merzbacher disease (PMD)?

Pelizaeus Merzbacher disease (PMD) is a rare X-linked genetic disorder that affects the central nervous system, specifically, with the part that makes up the myelin sheath (white matter) of the brain. Thus, PMD is one of the leukodystrophies. The myelin sheath is the protective covering of the nerves, and normally functioning is impossible without it. These neurologic problems in PMD get worse over time. PMD is divided into two types: classical and connatal.

What causes Pelizaeus Merzbacher disease (PMD)?

PMD is associated with abnormalities in the PLP1 gene, which is found on the X-chromosome. Due to the recessive nature of the mutation, the disorder affects mostly males, though female carriers could have mild signs of the disease that resolve with age.

What are the symptoms of Pelizaeus Merzbacher disease (PMD)?

Many areas of the central nervous system may be affected in PMD, such as the deep portions of the cerebrum, cerebellum, brain stem, and spinal cord. Resulting symptoms include the following:

• Inability to coordinate movement (ataxia)
• Involuntary muscle spasms (seizures)
• Sow, stiff leg movements
• Delays in reaching developmental milestones
• Late onset loss of motor abilities
• Progressive deterioration of intellectual ability
• Progressive skeletal deformities

Though there are two separated types of PMD, their features overlap, and severity is the main differentiating factor.

How is Pelizaeus Merzbacher disease (PMD) diagnosed?

PMD is diagnosed using a thorough clinical examination, a detailed patient and family history, and a variety of specialized tests, such as MRI scanning, to detect white matter deficiency. Recognizing these myelination defects early can greatly help subsequent treatment of the condition. To confirm a diagnosis, molecular genetic tests for the PLP1 gene is available.

What are the available treatments for Pelizaeus Merzbacher disease (PMD)?

Unfortunately, there is no standard treatment method nor particular regimen for individuals with PMD. Thus, treatment is symptomatic and supportive, based on preventing seizures or helping manage movement disorders. Anticonvulsants and supportive care are most often used for this purpose.

Where can I find more information on Pelizaeus Merzbacher disease (PMD)?

• National Organization for Rare Disorders (NORD)
• U.S. National Library of Medicine
• PMD Foundation