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Study: Tourette Genetic Updates

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  • Study: Tourette Genetic Updates

    • The Genetics of Tourette Syndrome
      by Adam T. McGruther

    In 1825, Georges Gilles de la Tourette, a French neurologist, diagnosed a woman with the first case of what would come to be known as Tourette Syndrome (TS).1 She exhibited symptoms such as facial tics, sudden outbursts of obscene language, and the repetition of things that were said to her. Since then, we have learned that TS is a genetically inherited disorder that may affect as many as 1 in 100 people, making it one of the most common genetic disorders known to man.1 In order to better explain TS, a case study will be utilized to give the reader a clear example of the implications of TS within a family.
    While much is known about the symptoms of TS, the mode of inheritance is still very complicated model. TS is believed to be an autosomal dominant disorder, meaning that the gene (or genes) that causes the disorder is located on one of the chromosomes numbered 1-22, and not on one of the sex chromosomes (X,Y).1 The reason that genes was placed in parenthesis is that recent studies have indicated that the disorder may not be limited to one gene, but have multifactoral implications.2 Since TS is a dominant disorder, those individuals who are homozygous for the disorder (TT, this refers to the presence of the gene(s) for TS on two paired chromosomes) are affected, as well as those who are heterozygous (Tt). However, the expressiveness of the gene(s), and hence the disorder is variable. Of the individuals who have the Tt genotype, only 2.2% of males and 0.3% of females are affected with the disorder.2 These numbers, however, are subject to change based on the interpretation of what qualifies as TS.

    Recent literature has expanded the scope of TS to include the following symptoms:2

    motor and/or vocal tics
    sleep disorders
    obsessive/compulsive behavior
    learning disabilities
    ADD (attention deficit disorder)
    Motor tics are generally the most common symptom associated with TS.

    In individuals with TS, multiple motor and vocal tics are usually observed, as well as some of the other behavioral symptoms mentioned. The tics can be classified as:3

    simple
    motor: eye blinking, shoulder shrugging, head jerking, facial grimacing
    vocal: throat clearing, yelping, tongue clicking, sniffing

    complex
    motor: jumping, twirling about, touching others, self-injurious behaviors
    vocal: uttering words or phrases out of context (obscenities or racial slurs)

    It is important to realize, however, while as many in 1 in 100 people may have TS (TT or Tt), very few actually manifest the complex tics or multiple symptoms.

    As mentioned before, the inheritance model is very complicated, and is best explained using a case study. Since the disorder is dominant, it tends to affect entire familial lines, and can be seen across the generations. Consider Mike and Carrie Riley; happy parents of six children, but confused by their children?s peculiar habits. Two of their boys, Greg and Ken, both tend to repeat what is said to them, and both have been in trouble in school for yelling out obscenities in class. Two of their other children, Alicia and Kate, both have problems with constant fidgeting, which disrupts their ability to sit still in school. For years Mike and Carrie had attributed their boy's behavior to childhood mischievousness, and dismissed their girl?s actions since both Mike and his mother, Rita, exhibited the same behavior. Mike and Carrie?s other two children, Joe and Cindy, have shown no signs of any behavior similar to their siblings.
    Mike's sister, Suzanne, and her husband, Adam, also have a couple of children with peculiar habits. Their son, Steve, is dyslexic, and is very poor at math. One of their daughters, Edie, constantly takes showers or is washing her hands. Their other child, Jenny, seems to exhibit no strange behavior or learning disabilities.
    While all of these cases seem to be unrelated, when one considers the broad definition of TS, a common thread can be seen throughout the Riley family. Suppose Rita is TT, meaning that she has full blown Tourette syndrome. If she married a man who was Tt, a carrier with no symptoms, any children they would have would be either TT or Tt. Mike, who has TS, is probably TT, and his sister, Suzanne, is probably Tt, but is not affected. Supposing that Adam is tt, he does not have TS and is not a carrier, Steve and Edie are probably Tt and are affected with TS. It is probable that their third child, Jenny, is also tt and therefore will not have TS. As for Mike?s children, since Carrie is probably tt, all of their children are Tt. However, since TS is expressed variably, not all of the children will necessarily develop the disorder (Joe and Cindy), and those that do have varying degrees of severity in their symptoms.
    Obviously there is a great deal of uncertainty in trying to diagnose Tourette syndrome. Many of it's symptoms are common to one or more other neurological disorders. Unfortunately, however, until the gene(s) responsible for Tourette syndrome is found, and a genetic test developed, much of the guesswork associated with this disorder will continue.

    REFERENCES:
    1Merz, Beverly, Journal of the American Medical Association, vol. 260, no. 18, pg 2619.
    2Walkup, J.T., LaBuda, M.C., Singer, H.S., Brown, J., Riddle, M.A., Hurko, O., American Journal of Human Genetics, 59:684-693, 1996.
    Source: http://www-personal.umd.umich.edu/~j....McGruter.html


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    Steve

    Dum spiro spero....While I breathe, I hope

    Tourette Canada Homepage
    If you enjoy the TC Forum, please consider a Tourette Canada membership
    Please visit our sister Forum: Psychlinks Psychology and Mental Health Support Forum

  • #2
    Study: Tourette Genetic Updates

    Steve,

    I have a question but really is for anyone. I have heard all my life that a % of people diagnosed with TS can "grow out of it" during their. Is this true and if it is, does that mean their genetics change or they just dont show symptoms anymore? Also, what is the common age for this "growing out of TS" (if true). Im 21 and have seen no real signs of it going away so am I too old and stuck with it for life?
    The other day at a local grocery store, I saw a rack with books on it and one of them said, "pregancy for dummies"............

    Comment


    • #3
      Study: Tourette Genetic Updates

      Adam,

      It's a good question, I've heard it too but I have never heard a good explanation of the mechanism of how people "grow out of it".

      I don't believe that one's genetic make up changes, so I suspect it may have to do with people learning suppression techniques as they age and mature.

      This would be an excellent question to be asked at the TSFC National Conference next week.
      Steve

      Dum spiro spero....While I breathe, I hope

      Tourette Canada Homepage
      If you enjoy the TC Forum, please consider a Tourette Canada membership
      Please visit our sister Forum: Psychlinks Psychology and Mental Health Support Forum

      Comment


      • #4
        Study: Tourette Genetic Updates

        Genetics can get even more complicated than the ones in the article. My father had Asperger syndrome, while I believe my mother may have had TS. My oldest brother has AS and TS (but won't admit it, knowing the symptoms now it's obvious to me), the next one (I'm the second oldest) definitely has AS and some tics (maybe TS, but everybody with AS has some tics as well), the next brother (I have six) has neither AS nor TS, my sister is a lot more autistic than me and has a lot of tics, the next brother has some tics but no AS, the one following him I can't figure out if he is insane, AS or what, he is so odd, and the youngest brother has possibly mild AS, and seems to have some tics as well.

        Since they're all in Germany, and I am here in Canada and never even heard of either TS or AS until a year and a half ago, I can't just go and observe them to figure out more details. But my family is sure pretty odd.

        And then there are my nephews and nieces..............I haven't figured them out yet, either, except for one. He's my older brother's boy (he's 14) and definitely AS.

        My husband must not have any genes for AS or TS in him at all, since our five children (four girls and one boy) have neither. Our son and our youngest daughter are obviously ADD, and the youngest has also inherited my dyscalculia (even worse than me), which is too bad. Mind you, I won't allow anybody to even suggest Ritalin for Susie (she is 13). The second youngest has a couple of tics, but nobody notices but me, because I now know what to look for.

        I think one of my granddaughters might have AS, but my daughter denies that possibility. At this point it doesn't matter, because the kid is only 3. And she is homeschooling her kids, anyway, individualizing their schooling to what works for each of them. So, nobody is going to care until high school the earliest.

        Okay, I guess I am writing a book again. Once I get going, I can't stop.
        German citizen, married to a Canadian for 28 years, four daughters, one son, eight grandchildren (and one on the way).

        Comment


        • #5
          Study: Tourette Genetic Updates

          Wow I think the way those genetics work is really neat...So if I married someone who does not even carry the tourettes gene, then chances are that my kids would be carriers with no tourettes, or have mild tourettes.

          If only there was a genetic test that could tell us who is a carrier, or who is TT, so that there wouldn't be guesswork, or misdiagnosis.

          Hopefully that day will come soon!
          Steph
          ~be a miracle~

          Comment


          • #6
            Study: Tourette Genetic Updates

            Steph:

            I think that the more we make others aware of TS to closer we will be to proper testing and funding for more testing to get the answers we need.

            TS is just as important as any other disorder and should be on the front burner for research.
            PJK

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            • #7
              Study: Tourette Genetic Updates

              So if I married someone who does not even carry the tourettes gene, then chances are that my kids would be carriers with no tourettes, or have mild tourettes
              .

              Hi Steph

              There are no guarantees in life. The fact is that I have mild TS and my husband does not and no one that we can see (note the word "see" vs "is diagnosed") in his family has TS. Yet, I produced 4 boys and to date 2 have TS and it is more severe than mine. The others definitely show symptoms of the associated disorders (they are only 5 yrs old). I would suspect that my husband (although not willing to admit) has ADHD. So if the day comes that the research creates a test to identify carriers of these disorders, then I wonder how that would impact how people will plan their families. I personally would not have done anything differently had I known years ago. Mothering children with TS is extremely challenging but the rewards far surpass the challenges. I personally feel that you are only dealt what you can handle.

              Steph just imagine the dating scene... with all the other things people these days have to worry about as they date and search for that perfect partner... they start asking their significant others to be screened to see if they are carriers of "genetic, neurological disorders" :P :P hummm! If he or she discovered they were carriers, then do you end the relationship in search of someone else or plan to not have children? There are worst things in life that people can have than TS, so when life hands you lemons, you make lemonade.

              Just food for thought
              Janet

              TSFC Homepage

              Comment


              • #8
                Study: Tourette Genetic Updates

                PJK,
                I agree with you that TS should be on the front burner for research and it is very unfortunate that it is not very commonly advertised. I myself had only heard of tourettes from an episode of TV I watched when I was younger, before I found out I had TS. It definitely needs to brought into the spotlight more.

                Janet,
                That is very interesting the way that the TS gene was passed on in your family, thanks for sharing it with me. I of course would not decide not to marry or date someone just because they were carriers of the gene as well, but it might make me think twice about having children, and consider adopting children instead. Not to say that there is something wrong with kids with TS (as I am one of them obviously), I am just not sure that I would be able to handle raising them since it would be harder...but I guess we will see when the time comes! Again, thanks for sharing!
                Steph
                ~be a miracle~

                Comment


                • #9
                  Study: Tourette Genetic Updates

                  If the gene research could be trusted to produce good things, I would think it's great they're doing it. But look at what happened with Down's Syndrome. They were claiming they were figuring out which genes caused it, to be able to help the kids who had it. But what did they really end up doing? Their 'treatment' consists now of screening babies in the womb, and aborting them.

                  When is the last time you saw a child with Down's Syndrome? I rarely see any now. When I was younger there were a lot more. That's because not many are born any more.

                  So, if they find that autism or Tourette gene some day (or I should say, genes, because it's not likely just one), will they just try to identify children earlier to be able to help them, or will they instead want to abort them? I bet they'd want to get rid of them before being born, it's a lot cheaper to prevent the births, than to help the people who have it.
                  German citizen, married to a Canadian for 28 years, four daughters, one son, eight grandchildren (and one on the way).

                  Comment


                  • #10
                    Study: Tourette Genetic Updates

                    Steph and PJK,

                    Believe me, I have had this discussion with steve and others many time. There are too many disorders that do not recieve enough attention but than other less affected "stuff" is more talked about. Again last time I used AIDs, and while I mean no disrespect towards anyone with it and hope for a cure soon, TS is said to affect more and I did nothing to get TS but AIDs is very preventable but it gets all the attention and money for research and time on MTV for awarness. And TS isnt it, in America, diabetes is becoming a huge problem but just now is getting some recognition. I dont want to sound like a mean person, I just dont think that if the problem can kill you it gets all the funding and research but if its not a sure death than your on your own. Ok, now I have vented, sorry. Again, I mean no offense towards anyone with AIDs or any disease, I just want more awarness for TS and other disorders.
                    The other day at a local grocery store, I saw a rack with books on it and one of them said, "pregancy for dummies"............

                    Comment


                    • #11
                      Study: Tourette Genetic Updates
                      • Is Tourette Syndrome inherited?

                      Evidence from twin and family studies suggests that TS is an inherited disorder. Although early family studies suggested an autosomal dominant mode of inheritance (an autosomal dominant disorder is one in which only one copy of the defective gene, inherited from one parent, is necessary to produce the disorder), more recent studies suggest that the pattern of inheritance is much more complex.

                      Although there may be a few genes with substantial effects, it is also possible that many genes with smaller effects and environmental factors may play a role in the development of TS. Genetic studies also suggest that some forms of ADHD and OCD are genetically related to TS, but there is less evidence for a genetic relationship between TS and other neurobehavioral problems that commonly co-occur with TS.

                      It is important for families to understand that genetic predisposition may not necessarily result in full-blown TS; instead, it may express itself as a milder tic disorder or as obsessive-compulsive behaviors. It is also possible that the gene-carrying offspring will not develop any TS symptoms.

                      The sex of the person also plays an important role in TS gene expression. At-risk males are more likely to have tics and at-risk females are more likely to have obsessive-compulsive symptoms.

                      People with TS may have genetic risks for other neurobehavioral disorders such as depression or substance abuse. Genetic counseling of individuals with TS should include a full review of all potentially hereditary conditions in the family.

                      • What is the prognosis?

                      Although there is no cure for TS, the condition in many individuals improves in the late teens and early 20s. As a result, some may actually become symptom-free or no longer need medication for tic suppression.

                      Although the disorder is generally lifelong and chronic, it is not a degenerative condition. Individuals with TS have a normal life expectancy. TS does not impair intelligence. Although tic symptoms tend to decrease with age, it is possible that neurobehavioral disorders such as depression, panic attacks, mood swings, and antisocial behaviors can persist and cause impairment in adult life.

                      Source:
                      Office of Communications and Public Liaison
                      National Institute of Neurological Disorders and Stroke
                      National Institutes of Health
                      Bethesda, MD 20892
                      All NINDS-prepared information is in the public domain and may be freely copied.
                      Steve

                      Dum spiro spero....While I breathe, I hope

                      Tourette Canada Homepage
                      If you enjoy the TC Forum, please consider a Tourette Canada membership
                      Please visit our sister Forum: Psychlinks Psychology and Mental Health Support Forum

                      Comment

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