Pelizaeus-Merzbacher Disease

What is Pelizaeus-Merzbacher disease?

Pelizaeus-Merzbacher disease (PMD) is a rare condition that’s usually genetic and affects your brain and spinal cord. It often causes problems with movement or muscle function.

Some people with PMD also experience developmental delays. PMD is progressive, meaning the symptoms worsen over time.

How does Pelizaeus-Merzbacher disease affect my body?

PMD is a type of genetic disease called a leukodystrophy. Leukodystrophies are conditions that affect your nervous system’s white matter, including myelin, the protective covering over your nerves. In PMD, your body doesn’t create enough myelin.

Who does Pelizaeus-Merzbacher disease affect?

PMD affects more men and people assigned male at birth than women and people assigned female at birth. It is an X-linked genetic disorder, meaning it occurs because of a mutation on one X chromosome.

Men are born with one X and one Y chromosome, while women have two X chromosomes. If the mutation that causes PMD occurs on the X chromosome in a man, he will develop the condition. If the mutation occurs on one X chromosome in a woman, she usually still has one functioning X chromosome. She may have less severe PMD symptoms or not develop the condition at all.

What are the types of Pelizaeus-Merzbacher disease?

There are two types of Pelizaeus-Merzbacher disease:

• Classic Pelizaeus-Merzbacher disease is most common. Symptoms develop in a baby’s first year of life. Classic PMD usually causes muscle and movement problems. People with classic PMD develop typical intellectual skills until around adolescence when development stops. People may slowly lose intellectual abilities after adolescence.
• Connatal Pelizaeus-Merzbacher disease is less common and more severe. Severe movement problems, poor growth, feeding problems and seizures develop in infancy. People with connatal PMD typically never develop walking skills. Many also have difficulty speaking, although they can usually understand others.

How common is Pelizaeus-Merzbacher disease?

Pelizaeus-Merzbacher disease is rare. In the United States, experts estimate that up to 1 in 200,000 men and people assigned male at birth have the condition. It occurs even less often in women and people assigned female at birth.

What are the symptoms of Pelizaeus-Merzbacher disease?

Pelizaeus-Merzbacher disease symptoms may include:

• Balance problems.
• Developmental delays.
• Feeding problems.
• High-pitched breathing (stridor).
• Involuntary eye movements (nystagmus).
• Involuntary tensing or jerking movements (dystonia).
• Poor weight gain.
• Weak muscles (hypotonia).

What causes Pelizaeus-Merzbacher disease?

Pelizaeus-Merzbacher disease usually occurs because of a change (mutation) in the PLP1 gene. You inherit this gene mutation from one or both parents.

Up to 20% of men and people assigned male at birth with PMD don’t have the PLP1 gene mutation. Some of them have a mutation in the GJC2 gene, or they may have PMD for no known reason.

How is Pelizaeus-Merzbacher disease diagnosed?

Your child’s healthcare provider may suspect PMD based on symptoms. They may use tests to confirm the diagnosis, including:

• Imaging tests, such as MRIs, to see if your child has low amounts of myelin.
• Genetic tests, such as blood tests, to check for the gene mutation that causes PMD.

How is Pelizaeus-Merzbacher disease treated?

There’s no cure for Pelizaeus-Merzbacher disease. Treatment focuses on improving quality of life and may include:

• Medications to reduce muscle spasms or seizures.
• Physical or occupational therapy to increase balance, strength and motor control.
• Eye treatments such as glasses or surgery to correct involuntary eye movements.
• Counseling with a licensed mental health provider to increase healthy coping skills and deal with the emotional effects of having a genetic disease.

How can I reduce my risk of Pelizaeus-Merzbacher disease?

There’s no way to prevent Pelizaeus-Merzbacher disease. If you have PMD or think you could be a carrier for it, you may consider genetic testing.

A genetic test looks for the gene mutation that causes PMD. A genetic counselor can help you understand the test results, including the risk of passing PMD to your children.

What is the prognosis of Pelizaeus-Merzbacher disease?

The prognosis for PMD varies depending on how severe the symptoms are. Severe symptoms usually continue to worsen, leading to a shortened lifespan.

However, some people live a typical lifespan and have mild symptoms that don’t affect their daily activities very much. Your healthcare provider can help you understand how Pelizaeus-Merzbacher disease may affect you or your child’s life.

What questions should I ask my doctor?

If you or your child has Pelizaeus-Merzbacher disease or you think you could, you may also want to ask a healthcare provider:

• What is the most likely cause of Pelizaeus-Merzbacher disease?
• What tests diagnose Pelizaeus-Merzbacher disease?
• What are the treatments for Pelizaeus-Merzbacher disease?
• What are the chances that I’ll pass Pelizaeus-Merzbacher disease to my children?

A note from Cleveland Clinic

It may be overwhelming to learn your child has Pelizaeus-Merzbacher disease. Treatment may vary depending on the type and severity of symptoms. Some people with PMD have mild symptoms that don’t significantly affect their abilities or lifespan. Talk with your healthcare provider to develop a treatment plan that works for you and your family.