This is an interesting, short question-and-answer on the Genetic and Rare Diseases Information Center (part of NIH) about the inheritability of progressive supranuclear palsy (PSP), from September 2012.
Robin
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rarediseases.info.nih.gov/diseases/7471/progressive-supranuclear-palsy/cases/36421
Progressive supranuclear palsy
Genetics and Rare Diseases Information Center (part of NIH)
Last updated 9/12/2012
Question: My identical twin sister has been diagnosed with progressive supranuclear palsy (PSP). As it seems this disease may have a genetic cause, what is the chance that I would also develop PSP? And within what timeframe?
Answer: The following information may help to address your question:
What is the chance of developing progressive supranuclear palsy if a relative is affected?
Researchers do not yet completely understand the causes of progressive supranuclear palsy (PSP), so it is not possible to predict the chance of a relative developing the condition if one family member has been diagnosed. Most of the time, only one person in a family develops PSP. It is not very common to have multiple members of a family develop PSP. One study found that 7% of individuals with PSP had a family history of potentially related conditions (including dementia or parkinsonism), which suggests there may be a shared genetic risk factor.[1][2]
A few genetic risk factors (particularly a gene called MAPT) are known to play a role in the development of PSP.[3][4] However, these genetic risk factors have only been found in a few families. Researchers suspect that there are other genetic factors that haven’t been found yet that also contribute to progressive supranuclear palsy.
If a family member has a known genetic risk factor for progressive supranuclear palsy, what is the chance a relative has inherited it?
Close relatives such as parents, siblings, and children of an affected individual have a greater chance of sharing a genetic predisposition than do aunts, uncles, grandparents or cousins. Identical twins share their entire DNA, so they should have the same genetic risk factors.
If an individual inherited a known risk factor, what is the chance of developing progressive supranuclear palsy?
Having a genetic risk factor increases the chance of developing progressive supranuclear palsy (PSP); it does not guarantee that an individual will develop this disease at some point in their lifetime. The exact risk of developing PSP in an individual with a genetic predisposition is currently unknown.[5]
What is the average age at diagnosis for progressive supranuclear palsy?
Individuals with progressive supranuclear palsy usually experience the first symptoms of this disease while in their 60s.[1]
We hope this information is helpful. We strongly recommend you discuss this information with your doctor. If you still have questions, please contact us.
Warm regards,
GARD Information Specialist
References
1. Progressive supranuclear palsy. Genetics Home Reference. March 2011; http://ghr.nlm.nih.gov/condition/progressive-supranuclear-palsy. Accessed 9/7/2012.
2. Donker Kaat L, Boon AJ, Azmani A, Kamphorst W, Breteler MM, Anar B, Heutink P, van Swieten JC. Familial aggregation of parkinsonism in progressive supranuclear palsy. Neurology. 2009; 73:98-105. http://www.ncbi.nlm.nih.gov/pubmed/19458322. Accessed 9/12/2012.
3. Rojo A, Pernaute RS, Fontán A, Ruíz PG, Honnorat J, Lynch T, Chin S, Gonzalo I, Rábano A, Martínez A, Daniel S, Pramstaller P, Morris H, Wood N, Lees A, Tabernero C, Nyggard T, Jackson AC, Hanson A, de Yébenes JG. Clinical genetics of familial progressive supranuclear palsy. Brain. 1999; 122:1233-1245. http://www.ncbi.nlm.nih.gov/pubmed/10388790. Accessed 9/6/2012.
4. Dickson DW, Rademakers R, Hutton ML. Progressive supranuclear palsy: pathology and genetics. Brain Pathology. 2007; 17:74-82. http://www.ncbi.nlm.nih.gov/pubmed/17493041. Accessed 9/6/2012.
5. Litvan I. Update on epidemiological aspects of progressive supranuclear palsy. Movement Disorders. 2003; 18:S43-S50. http://www.ncbi.nlm.nih.gov/pubmed/14502655. Accessed 9/6/2012.