![]() Feelings of guilt have also been reported in the research literature in cases where people are found not to be carriers of the disease. This can sometimes lead to feelings of depression or anxiety. However, it is possible that if one is found to be a carrier of the disease, this could lead to worries about what the future may be like. The results from genetic testing could provide reassurance and relief from uncertainty, particularly in cases where not knowing presents its own challenges. It is important to bear in mind that if you have a predictive genetic test for CADASIL and you are found to be a carrier, that does not mean that you have CADASIL but you will have an increased risk of developing the condition in the future. There are numerous psychological and emotional consequences of genetic testing and it may be helpful to consider these before one goes through the procedure. ISSUES TO CONSIDER WHEN UNDERTAKING GENETIC TESTING You will also have the opportunity to discuss this with your friends and family. This allows us to give you all the information that you need and gives you time to go away and think about the implications of your decision and how you might deal with the result. Our usual protocol for undertaking predictive testing involves at least two visits to the clinic prior to undertaking the test. Whether or not to have a predictive genetic test is a difficult but important decision for each individual who is suspected of being at-risk of CADASIL. An individual without the gene change is very unlikely to develop CADASIL. We could not say whether the individual would be affected by strokes, migraines or depression, or any combination of the three symptoms. It is not possible by doing the genetic test to determine whether an individual would be affected at all, or the age at which they may be affected. An individual who inherits a gene change will almost certainly, at some stage in their life, develop some signs and symptoms of the disease. Each individual with a first degree relative affected by CADASIL has a 1 in 2 chance of having the same gene change. This form of genetic testing is undertaken on individuals who have no obvious signs of CADASIL but have an affected relative (usually a first degree relative – i.e. Once a gene change has been found in an affected individual, predictive testing of other, unaffected, relatives is possible. This allows discussion about the diagnosis and future management. The individual being tested would normally be seen in the clinic to receive the results of the test. Testing in the laboratory takes approximately six to eight weeks. Genetic testing for CADASIL requires only a blood sample or in some cases a sample of spit can be used. In individuals showing characteristic signs of the disease on the MRI scan, and having symptoms such as migraine, the chance of finding a NOTCH3 gene change is about 90%. If a change is found within the NOTCH3 gene then this makes the diagnosis 100% certain. This means that if you are having symptoms of CADASIL or you have had an MRI scan of the brain or a skin biopsy and the findings suggest a diagnosis of CADASIL then a genetic test can be used to confirm the diagnosis. This form of testing is undertaken where there is a strong clinical suspicion that an individual has CADASIL. For this reason routine genetic testing of the whole gene is not always performed in CADASIL. Most of the abnormalities tend to occur in certain parts of the gene and many laboratories only screen these parts of the gene. We have carried out studies to show that limited screening can pick up about 90% of NOTCH3 gene changes in a UK population. However, increasingly with new technology laboratories are screening the whole gene to look for abnormalities. Testing for this can be a very time-consuming process. In CADASIL, there is an abnormality (mutation) in only one of these. However, this gene is made up of many thousands of building blocks (base pairs). In CADASIL the abnormalities that occur are all within one gene which is called NOTCH3. Changes in the NOTCH3 gene are known to be associated with the development of CADASIL.įor this reason, if we can detect an abnormality on genetic testing, we can be 100% sure that someone has CADASIL. In both cases, testing of a gene known as NOTCH3 is undertaken. Genetic testing takes two forms: diagnostic and predictive.
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