Progressive supranuclear palsy

What causes progressive supranuclear palsy?

While progressive supranuclear palsy (PSP) is usually sporadic, some cases run in families. In most cases, the genetic cause is unknown, but some are due to mutations or "variations" in the _MAPT _gene.

The MAPT gene gives the body instructions to make a protein called tau. This protein is found in nerve cells (neurons) in the brain and in other parts of the nervous system. It plays a part in putting together and stabilizing components of the structure of cells, helping cells to keep their shape, and aiding in cell division and the transport of materials. It appears that gene mutations or variations that affect the function of the tau protein cause PSP, or cause an increased risk for a person to develop PSP.

Abnormal tau is also found in people with PSP who don't have MAPT mutations. Therefore, researchers think that additional genetic and environmental factors contribute to the development of PSP. However, other specific genes that may be involved have not yet been identified.

Last updated on 05-01-20

How is progressive supranuclear palsy diagnosed?

Progressive supranuclear palsy (PSP) is often hard to diagnose because its symptoms can be similar to those of other, more common movement disorders. It may also be hard to diagnose because some of the most characteristic symptoms may develop late, or not at all.

A diagnosis of PSP is currently based on the signs and symptoms present (clinical features). Identifying early gait instability and difficulty moving the eyes (the hallmark of the disease), as well as ruling out other conditions, are most important. There is no laboratory test or imaging study that is diagnostic. Identifying neurofibrillary tangles (aggregates of tau) in their characteristic distribution aids in the diagnosis.

Last updated on 05-01-20

Is genetic testing available for progressive supranuclear palsy?

Progressive supranuclear palsy (PSP) is usually sporadic (not inherited), but in rare cases it can be inherited. While the genetic cause of PSP not usually known, it can be caused by a mutation in a gene called MAPT. To our knowledge, MAPT is currently the only gene for which clinical genetic testing for PSP is available. This means that if a person with PSP is found to have a disease- causing mutation in the MAPT gene, genetic testing of other family members for the same mutation in this gene may be available. Each child of a person with PSP caused by a MAPT mutation has a 50% chance to inherit the mutated gene. However, if a person with PSP does not have a mutation in the MAPT gene (which is most often the case), clinical genetic testing for other family members is not available.

The Genetic Testing Registry (GTR) provides information about the genetic tests available for PSP. People interested in genetic testing for PSP are encouraged to speak with a genetics professional for additional information.

Last updated on 05-01-20

Is progressive supranuclear palsy inherited?

Progressive supranuclear palsy (PSP) is usually a sporadic condition (not inherited), occurring in people with no family history of PSP. However, in more recent years it has been found that in rare cases, PSP is familial. It has also been found that some people with PSP have close relatives with dementia or parkinsonism.

Cases of familial PSP caused by a mutation in the MAPT gene have been reported. MAPT mutations are also known to be responsible for other familial tauopathies. Currently, the proportion of people with PSP who have a MAPT mutation is unknown.

PSP caused by MAPT mutations is inherited in an autosomal dominant manner. This means that having a mutation in only one copy of the gene in each cell is enough to cause features of the condition. In some cases, an affected person inherits the mutated gene from an affected parent. In other cases, the mutation occurs for the first time in a person with no family history of the condition. This is called a de novo mutation.

When a person with a mutation causing an autosomal dominant condition has children, each child has a 50% (1 in 2) chance to inherit that mutation.

While other locations on chromosomes have been linked to familial PSP, to our knowledge, no other causative genes have been identified. There may also be genes (including MAPT ) in which "variants" increase a person's risk to develop PSP. In these cases, the condition itself is not inherited, but a predisposition to developing PSP or a related condition may be inherited.

Because there are likely unidentified genetic causes of PSP, if the genetic cause in a family is unknown, we cannot estimate the likelihood that PSP might recur. Our understanding of the genetics of PSP is expanding, and studies are ongoing.

People with a personal or family history of PSP with questions about recurrence risks or genetic testing are encouraged to speak with a genetics professional.

Last updated on 05-01-20

What is the long-term outlook for people with progressive supranuclear palsy?

Progressive supranuclear palsy (PSP) gets progressively worse. Most people become dependent for care within three or four years from onset, and quality of life is significantly reduced. However, with good attention to medical and nutritional needs, it is possible for many people with PSP to live a decade or more after the first symptoms appear. The condition predisposes people to serious complications such as pneumonia (the most common cause of death) secondary to difficulty in swallowing (dysphagia). Other complications that people may experience include choking, head injury, and fractures caused by falls.

Last updated on 05-01-20

How might progressive supranuclear palsy be treated?

There are currently no treatments that alter the course of disease for people with progressive supranuclear palsy (PSP), and no drugs that provide significant relief of symptoms. However, supportive treatment may be helpful and may include:

  • Management of dysphagia and dysarthria with the help of dietitians as well as speech and language therapists
  • Early occupational therapy to promote longer independence in performing activities of daily living
  • The use of mirror-prism lenses for those with severe limitation of extraocular movements to read and feed themselves
  • The use of eyelid crutches, alone or in combination with botox therapy, for inability to open the eyes and blepharospasm
  • Physical therapy for symptomatic treatment of postural instability and falls, including gait and balance training

A surgical procedure called a gastrostomy may be necessary when there are swallowing disturbances or a high risk of severe choking.

Last updated on 05-01-20

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