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Progressive Multifocal Leukoencephalopathy (PML)

Article
Brain & Nerve
Diseases & Conditions
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Contributed byMaulik P. Purohit MD MPHJan 02, 2019

What are the other Names for this Condition? (Also known as/Synonyms)

  • PML (Progressive Multifocal Leukoencephalopathy)
  • Progressive Multifocal Leukoencephalitis

What is Progressive Multifocal Leukoencephalopathy? (Definition/Background Information)

  • Progressive Multifocal Leukoencephalopathy (PML) is a rare, but fatal brain disease caused by reactivation of the polyomavirus JC in the central nervous system (CNS) of immunocompromised individuals. The disease damages the myelin, material that covers and protects the nerves in the brain
  • The polyomavirus is a generally harmless virus, except in those with weak immune systems. In such individuals, PML causes clumsiness with progressive weakness, speech and vision defects, difficulties with memory, and personality changes
  • A diagnosis of PML would include imaging studies of the brain (CT and MRI scan) and examination of cerebrospinal fluid for the presence of the JC virus
  • There is no specific treatment for Progressive Multifocal Leukoencephalopathy, which leads to acute brain and neurological dysfunction. The prognosis of the condition is very poor, with death typically occurring within 1 to 3 months of disease onset

Who gets Progressive Multifocal Leukoencephalopathy? (Age and Sex Distribution)

  • Progressive Multifocal Leukoencephalopathy can affect any individual; but, it is more common in adults
  • The condition is rare in children
  • There is no gender, racial, or ethnic predilection

What are the Risk Factors for Progressive Multifocal Leukoencephalopathy? (Predisposing Factors)

The risk factors associated with Progressive Multifocal Leukoencephalopathy include individuals with compromised immune system such as:

  • AIDS and HIV-infected individuals
  • Those who have undergone recent organ transplant
  • Those undergoing chemotherapy
  • Individuals taking medications to suppress the immune system for a variety of reasons, such as for rheumatoid arthritis or multiple sclerosis
  • Individuals with cancers such as leukemia and lymphoma (Hodgkin’s lymphoma)
  • Individuals with conditions such as sarcoidosis and systemic lupus erythematosus

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Progressive Multifocal Leukoencephalopathy? (Etiology)

  • Progressive Multifocal Leukoencephalopathy is a rare viral infection that fatally affects the brain. It develops only in individuals with poor or severely affected immune system
  • The virus responsible for the condition is the JC Virus (JCV). The virus is latently present in most humans (in about 80-90% of them), who normally contract them by of before age 10. However, the virus remains inactive and is harmless, since healthy humans have a strong and robust immune system
  • PML is caused by the reactivation of the polyomavirus JC, due to certain medications or immunodeficiencies, leading to a progressive damage of the central nervous system. The myelin sheath that covers the nerve cell is destroyed (demyelination) by the virus impairing nerve impulse transmission
  • PML is also considered to be caused by pharmacological agents such as efalizumab, belatacept, rituximab, natalizumab, infliximab, tacrolimus, chemotherapy drugs, and  corticosteroids

What are the Signs and Symptoms of Progressive Multifocal Leukoencephalopathy?

The signs and symptoms of Progressive Multifocal Leukoencephalopathy are related to the location and amount of damage in the brain. These include:

  • Clumsiness due to coordination loss (ataxia)
  • Progressive weakness, headaches
  • Speech and vision defects; aphasia (loss of language capability)
  • Memory-related disorders
  • Personality and cognitive changes
  • Seizures
  • Paralysis

How is Progressive Multifocal Leukoencephalopathy Diagnosed?

The diagnosis of Progressive Multifocal Leukoencephalopathy may include a detailed evaluation of medical history and a thorough physical exam. Other diagnostic tests performed to confirm PML may include:

  • MRI scan of the brain, which uses magnetic waves to take pictures of the brain structure and evaluate the extent of damage caused by the JC virus
  • Spinal tap: A small amount of cerebrospinal fluid (CSF) is removed and examined for the presence of JC virus in the brain
  • Brain biopsy: This procedure is very rarely used

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Progressive Multifocal Leukoencephalopathy?

The possible complications associated with Progressive Multifocal Leukoencephalopathy include:

  • Progressive weakness of the body with complete paralysis
  • Speech defects with eventual aphasia (complete loss of speech)
  • Memory-related signs and symptoms
  • balance and co-ordination difficulties

How is Progressive Multifocal Leukoencephalopathy Treated?

There is no specific treatment of Progressive Multifocal Leukoencephalopathy (PML). Current available treatment options include:

  • In some AIDS patients, highly active antiretroviral therapy (HAART) has been effective
  • Other antiviral agents that are being experimented for this condition include cidofovir and interleukin
  • Cytarabine also known as ARA-C, a chemotherapy drug, is used on non-AIDS patients with PML, and it has helped stabilize the neurological condition of patients
  • Mefloquine, an anti-malarial drug was also administered in PML patients on an experimental basis. It has helped eliminate the virus from the patient’s body and stabilize some of the neurological conditions

How can Progressive Multifocal Leukoencephalopathy be Prevented?

  • The JC polyomavirus is latently found in most humans; the virus affects a large percentage of the population
  • The viral infection can be prevented by averting immunodeficiency situations, by providing suitable treatment and medical care after major surgeries (organ transplant), or when a body immunity system is weakened by other illnesses
  • The key preventive strategy against Progressive Multifocal Leukoencephalopathy is to keep the immune system healthy

What is the Prognosis of Progressive Multifocal Leukoencephalopathy? (Outcomes/Resolutions)

  • The prognosis for progressive multifocal leukoencephalopathy is very poor. 30-50% of the individuals diagnosed with PML die after 1-3 months of onset of the disease; others are affected by severe and irreversible neurological defects causing disabilities
  • There have been cases where individuals are reported to have survived for months to years after disease onset. Typically, 10% of the cases survive over 12 months

Additional and Relevant Useful Information for Progressive Multifocal Leukoencephalopathy:

The JC virus is a common virus belonging to the family of polyomavirus that is found in most human beings (almost 85% of them). It is named after John Cunningham, a patient in whom it was diagnosed in the early 70s.

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Maulik P. Purohit MD MPH

Assistant Medical Director, Medical Editorial Board, DoveMed Team

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