Wednesday, August 3, 2022

Is There A Genetic Test For Parkinson’s

Other Causes Of Parkinsonism

Ask the MD: Genetic Testing in Parkinson’s Disease

“Parkinsonism” is the umbrella term used to describe the symptoms of tremors, muscle rigidity and slowness of movement.

Parkinson’s disease is the most common type of parkinsonism, but there are also some rarer types where a specific cause can be identified.

These include parkinsonism caused by:

  • medication where symptoms develop after taking certain medications, such as some types of antipsychotic medication, and usually improve once the medication is stopped
  • other progressive brain conditions such as progressive supranuclear palsy, multiple systems atrophy and corticobasal degeneration
  • cerebrovascular disease where a series of small strokes cause several parts of the brain to die

You can read more about parkinsonism on the Parkinson’s UK website.

Page last reviewed: 30 April 2019 Next review due: 30 April 2022

Research Into Genes And Parkinsons

Our major effort now is understanding how mutations in these genes cause Parkinsons disease, says Dawson. SNCA, the gene responsible for making the protein that clumps in the brain and triggers symptoms, is particularly interesting.

Our research is trying to understand how alpha-synuclein works, how it travels through the brain, says Dawson. The latest theory is that it transfers from cell to cell, and our work supports that idea. Weve identified a protein that lets clumps of alpha-synuclein into cells, and we hope a therapy can be developed that interferes with that process.

Targeting Parkinsons-Linked Protein Could Neutralize 2 of the Diseases Causes

Researchers report they have discovered how two problem proteins known to cause Parkinsons disease are chemically linked, suggesting that someday, both could be neutralized by a single drug designed to target the link.

Genetic Testing And Parkinson’s

Research suggests that a combination of genetic and environmental factors leads to the development of Parkinsons in most cases. Research continues to determine how these factors interact, and the extent to which each is involved. Current research suggests that only about five percent of cases of Parkinsons can be definitely linked to a genetic cause.

Although there are a few families in which more than one person develops Parkinsons, it is rare for the condition to be passed from one generation to the next. Most research suggests that the condition develops as a result of genetic susceptibility and an external trigger, such as environmental chemicals. Exactly how this happens is not yet clear.

Researchers have so far identified a number of genes that seem to be linked to Parkinsons, including the parkin, PINK1, PARK7, SNCA and LRRK2 genes. It is important to note, however, that a mutation of one of these genes does not necessarily mean that the condition will develop.

Genetic testing for several Parkinsons genes is now quite widely available. From a medical point of view, this can help to confirm a diagnosis of Parkinsons. However, the decision to undergo genetic testing needs to be made carefully, as it may have implications for other family members. Knowing there is an increased risk of developing Parkinsons may cause unnecessary worry in people who may never go on to develop the condition.

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What Is Genetic Testing

Genes inside our cells carry the instructions for our physical attributessuch as hair and eye color, height, and the shape of our noses and kneesbut they also contribute to our risks for developing diseases.

We all carry the same genes, but within those genes there are differences, which we call variants, Mata says. The variants make us the individuals we are. If we think about our genetic information as a book, the genes would be the chapters, and the variants are the words. Sometimes these words have consequences, causing or increasing our risk to develop certain diseases. With genetic testing we look at those genes and try to find variants that could be potentially disease-causing, he says.

Mata explains that genetic variants are passed from generation to generation, so genetic testing, under the supervision of a genetic counselor, could be very helpful to determine a possible genetic cause of a disease.

The impact for the patient with Parkinson’s disease could be huge, as several clinical trials are ongoing for individuals with certain genetic variants,” Mata says. “This means that new therapies are being created targeting the biological cause of the disease, therefore potentially being much more effective in slowing or stopping the progression of the disease in that specific group of patients.”

Faqs: Genetics & Parkinsons

How To Test For Parkinsons

If I have Parkinson’s disease will my child get it too? Will I inherit Parkinson’s if my parent or grandparent has it?

Most people with Parkinson’s have no known genetic link. Their children will likely never develop Parkinson’s. There are some known genetic variations that increase the risk of getting Parkinson’s, but most people with these variations do not get Parkinson’s. Like many other diseases, Parkinson’s is a result of a complex interaction between genes and environmental factors.

In a small number of people , Parkinson’s is inherited and can affect multiple family members. Their children may have a higher risk of developing Parkinson’s. However, there is no guarantee they will develop PD.

What if my genetic test is positive for a Parkinson’s gene?

Scientists have identified several genetic mutations that can increase the risk of developing Parkinson’s. If someone tests positive for a mutation in a Parkinson’s gene, it does not necessarily mean they will develop PD. Some people who have mutations in the genes associated with Parkinson’s never develop PD. A person may inherit a hereditary genetic mutation that increases their risk for Parkinson’s however, they may also inherit other genes, be exposed to environmental factors or have lifestyle choices that offset the risk. Genetic testing is currently available for the following genes related to Parkinson’s: GBA, PARK7, SNCA, LRRK2, parkin and PINK1.

What can I do with my genetic test results?

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What Research Has Been Done And The Need To Improve:

CANTAB Connect for Parkinsons disease is a rapid, reliable, and highly sensitive system for academic research or clinical trials. The CANTAB battery has demonstrated potential advantages when compared to other neuropsychological tests, such as for detecting cognitive impairment in Parkinsons disease7 and also avoiding floor and ceiling effects. It is highly sensitive to disease progression, can discriminate cognitive impairment due to comorbid depression, and detects untoward effects of medications on cognition11-14. It has also been shown to predict conversion to dementia in patients with Parkinsons disease15. The use of CANTAB in research of Parkinsons disease is clinically relevant: cognitive decline measured by the battery correlates with loss of day-to-day functioning in patients with Parkinsons disease16.

Furthermore, CANTAB maximises scope for sample enrichment, and for demonstrating disease modifying capability of interventions.

There are currently over 125 peer-reviewed publications supporting the application of CANTAB in research of Parkinsons disease. To find out more, .

How Hereditary Is Parkinson’s Disease

If your mom or dad gets Parkinson’s disease, you might wonder if you’ll get it, too. The good news is that the chance of inheriting Parkinson’s disease is rare . Just how hereditary Parkinson’s disease is depends on the exact mutation involved.

There are two categories of genetic factors linked to Parkinson’s. The first is “causal,” meaning the gene itself is capable of bringing on the disease.

One example of a causal link to Parkinson’s disease can be found in the SNCA gene. Researchers know of at least 30 mutations on this particular gene that can cause Parkinson’s disease, especially in people younger than 50 years old.

The SNCA gene tells the body how to make a protein called alpha-synuclein. When the gene has a mutation, the body may produce too much alpha-synuclein or versions of the protein with an incorrect shape. Either of these problems can lead to alpha-synuclein to gather in the brain in clusters called Lewy bodies, which disrupt normal brain functioning. Lewy bodies are associated with Parkinson’s, along with a range of other diseases .

Not all genetic mutations cause Parkinson’s disease, though. “Associated” genetic factors for Parkinson’s increase a person’s odds of developing the disease, but aren’t directly responsible for it.

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“You’re susceptible, but you need something else present as well ,” Dr. Litvan says. “That could be other genes or it could be an environmental factor.”

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Genetics Testing In Parkinson’s Disease

Genetic testing in Parkinson’s disease can play an important role in diagnosing the illness. Scientists hope that the knowledge provided by genetics will ultimately help slow or stop its progression.

Genes are carried in our DNA, units of inheritance that determine the traits that are passed down from parent to child. We inherit about 3 billion pairs of genes from our mothers and fathers. They determine the color of our eyes, how tall we may be and, in some instances, the risk we have in developing certain diseases.

As a physician, I know the role that genetics plays in determining our health. The degree of influence that our genes have varies depending on the disease, but both environmental factors and genetics contribute to the development of illness to some extent.

Blood Test May Help Distinguish Parkinsons From Similar Diseases

The rising utility of genetic testing in Parkinsons disease

Researchers have found that people with Parkinsons disease have lower levels of a certain protein in their blood than people with similar diseases. The results suggest that testing for the protein might help doctors to accurately differentiate between PD and similar diseases early on. The study appears in the February 8 online edition of Neurology.

Because there are no definitive diagnostic tests for Parkinson’s, the diagnosis can be unclear especially early on in the disease. When diagnosis is uncertain, some people may be diagnosed with parkinsonism,” which refers to a category of diseases, including Parkinson’s, that cause slowness of movement, stiffness and rest tremor. Other diseases in the category include multiple system atrophy , progressive supranuclear palsy and corticobasal degeneration .

Earlier studies found that a spinal fluid test may help distinguish PD from these other diseases, but this test is difficult to do during a routine visit to the doctor.

Results

  • Blood levels of NfL protein were generally lower in people with PD and in healthy individuals than in people with other Parkinsonian disorders.
  • This result held both for those recently diagnosed and those who had been living with their disease for four to six years.
  • The test for NfL could not distinguish between MSA, PSP and CBD.

What Does It Mean?

References

Hansson O, Janelidze S, Hall S, et al. . Blood-Based NfL: A Biomarker for Differential Diagnosis of Parkinsonian Disorder. Neurology 88: 1-8

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Test Strength And Limitations

Test Strengths

It can detect the VPS35 c.1858G> A, p. variant, which is within the pseudogene region and is known to be challenging to detect by NGS technologies.

The strengths of this test include:

  • CAP accredited laboratory
  • CLIA-certified personnel performing clinical testing in a CLIA-certified laboratory
  • Powerful sequencing technologies, advanced target enrichment methods and precision bioinformatics pipelines ensure superior analytical performance
  • Careful construction of clinically effective and scientifically justified gene panels
  • Some of the panels include the whole mitochondrial genome
  • Our Nucleus online portal providing transparent and easy access to quality and performance data at the patient level
  • Our publicly available analytic validation demonstrating complete details of test performance
  • ~2,000 non-coding disease causing variants in our clinical grade NGS assay for panels
  • Our rigorous variant classification scheme
  • Our systematic clinical interpretation workflow using proprietary software enabling accurate and traceable processing of NGS data
  • Our comprehensive clinical statements

Test Limitations

This test does not detect the following:

  • Complex inversions
  • Gene conversions
  • Balanced translocations
  • Some of the panels include the whole mitochondrial genome but not all
  • Repeat expansion disorders unless specifically mentioned
  • Non-coding variants deeper than ±20 base pairs from exon-intron boundary unless otherwise indicated .

Racial Disparities Under The Microscope

When understanding the difference in PD incidence across racial and ethnic groups, Mata says environmental factors should be taken into consideration.

Non-genetic factors contribute to the development of the disease, and therefore these could play a role in the possible differences between populations, Mata says. For example, many Latinxs in the U.S. work in farming, where massive amounts of pesticides are used, and exposure to pesticides is an important environmental factor in the development of Parkinson’s disease.”

Mata stresses the importance of genetic testing for developing future treatment and understanding some of these differences.

We have to keep in mind that using genetic information to determine, for example, the best treatment, is a reality in many diseases and will soon be for some neurological disorders, Mata says. Therefore, if we dont include all populations in our studies, we will be accentuating already-existing health disparities.

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Genetic Testing Cannot Tell You If You Will Or Will Not Get Parkinsons

Parkinson’s is not linked to any single gene mutation that causes disease 100 percent of the time. If you do test positive for a PD-linked mutation, it does not mean you will absolutely get Parkinson’s. There are actions you can take, such as exercise, to lower risk. Conversely, if you test negative for a PD-linked mutation, you may still develop Parkinson’s. Other mutations and factors such as aging and environmental causes also contribute to risk. Science is working to better understand who does get Parkinson’s and why.

Genetic Testing Is Primarily For Research Not Care

Parkinsons disease

Genetic testing as part of a research study is not necessarily intended to provide you with personal medical information and, in some studies, you may not learn your results. As of this writing, even if you discover that you do carry a genetic mutation, these results will not significantly alter your personal medical care. Some studies are testing new therapies in mutation carriers. Your genetic status may allow you to participate in research studies, partnering with scientists to add to our existing knowledge about brain disease and help evaluate new treatments.

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Further Testing In Parkinson’s

In other situations, where perhaps the diagnosis is not as clear, younger individuals are affected, or there are atypical symptoms such as tremor affecting both hands or perhaps no tremor at all, further testing may help. For example, imaging can play a role in differentiating between essential tremor and Parkinsons. It can also be important to confirm what is initially a clinical diagnosis of Parkinsons prior to an invasive treatment procedure such as surgical DBS

Assay And Technical Information

Invitae is a College of American Pathologists -accredited and Clinical Laboratory Improvement Amendments -certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology .

Our sequence analysis covers clinically important regions of each gene, including coding exons and 10 to 20 base pairs of adjacent intronic sequence on either side of the coding exons in the transcript listed below, depending on the specific gene or test. In addition, the analysis covers select non-coding variants. Any variants that fall outside these regions are not analyzed. Any limitations in the analysis of these genes will be listed on the report. Contact client services with any questions.

Gene

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Bioinformatics And Clinical Interpretation

Bioinformatics

Clinical interpretation

We provide customers with the most comprehensive clinical report available on the market. Clinical interpretation requires a fundamental understanding of clinical genetics and genetic principles. At Blueprint Genetics, our PhD molecular geneticists, medical geneticists and clinical consultants prepare the clinical statement together by evaluating the identified variants in the context of the phenotypic information provided in the requisition form. Our goal is to provide clinically meaningful statements that are understandable for all medical professionals regardless of whether they have formal training in genetics.

Variant classification is the corner stone of clinical interpretation and resulting patient management decisions. Our classifications follow the ACMG guideline 2015.

The final step in the analysis is orthogonal confirmation. Sequence and copy number variants classified as pathogenic, likely pathogenic and variants of uncertain significance are confirmed using bi-directional Sanger sequencing or by orthogonal methods such as qPCR/ddPCR when they do not meet our stringent NGS quality metrics for a true positive call.

The Decision To Seek Genetic Testing Is A Personal One

Genetics & Parkinson’s Disease

Learning you carry a gene mutation that raises disease risk can be concerning for you and your family. The decision to seek genetic testing or to participate in genetic research deserves extra attention. A genetic counselor is trained to talk with you and help you gain a fuller understanding of what your results might mean for you and your family.

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What Are The Benefits Of Genetic Testing

ESCAPE is developing a new therapy for patients with Parkinson’s disease caused by a mutation in theLRRK2 gene. It is hoped that this therapy may be able to stop or slow the progression of the disease. Since most people with Parkinsonâs disease have never been tested for LRRK2 mutations, ESCAPE is providing free genetic testing via mail which is an at-home saliva test. If a patient is found to have a mutation in theLRRK2 gene they will be invited to take part in certain clinical studies for patients with Parkinson’s disease and this specific gene mutation.

What To Know About Genetic Testing

Genetic testing can help identify changes in our DNA that may be linked to Parkinsons. Learning your genetic status is a personal decision, but the results may help you take action in your health and advance science closer to cures.

Some of the greatest strides in understanding Parkinsons disease and developing new therapies have come from the study of human genetics. Read more below on what to consider before genetic testing and where to access this type of testing.

Navigating Clinical Trials

The Michael J. Fox Foundation’s guide and related materials will help you learn the basics of clinical research and gain an understanding of the valuable contributions made by study volunteers. Learn about genetic research and testing in Chapter 3 of the guide.

Ask the MD

Rachel Dolhun, MD, is a board-certified movement disorder specialist and The Michael J. Fox Foundation’s Senior Vice President of Medical Communications. In this short video, she explains what to expect when you opt for genetic testing and genetic counseling in Parkinson’s.

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