Genetics Role in Huntington Disease: A Case Study

In honor of Huntington disease (HD) awareness month, I thought I would present a case study highlighting some of the common issues families encounter with HD and how genetics plays a factor in this disease.

The Smith Family

Jane Smith is a healthy and happy 16-year-old junior in high school who lives at home with her parents and younger brother Tom. Over the past few months, Jane has noticed that her father, Bill, has been irritable and moody, which is very different from his normal personality. Jane’s mother, Robyn, has tried to reassure Jane that her father’s bad moods have been a result of Bill’s mother’s recent suicide. Bill’s mother, Mary, was widowed after Bill’s father died from a heart attack at 68. Mary developed what she thought was Parkinson disease and made the decision to end her life. Bill, understandably, had taken his mother’s death hard, however, Jane was worried that something else was wrong. Jane had noticed that her father developed an unusual gait, that is, he had begun to walk a bit different recently. In addition to the unusual gait, Jane also noticed that her father has been a little forgetful, which is very unlike Bill. 

Several months later, after the summer, Jane begins her senior year at high school. Her dream is to become a pilot after she finishes school, however, this dream may no longer be possible. Bill’s unusual symptoms worsened over the summer break and he lost his job as a mailman. Because of the drastic changes in his health, he finally sought medical help. His family physician referred him to see a neurologist. After assessing his symptoms, his neurologist ordered Huntington disease testing. Unfortunately, the results were positive. This was not good news because it meant that his symptoms were likely to get worse. It also meant that he is likely to die from HD in the next decade. But the most upsetting news was that because HD is hereditary, both Jane and her brother Tom have a one in two chance of developing HD in their lifetime. It was most likely that their grandmother did not have Parkinson disease, but HD and now they know they are also at risk. 

Robyn arranged for Jane to meet with a genetic counselor named Nick who specializes in neurogenetics. At the first appointment, Jane and her mother met with Nick and discussed everything that encompasses HD. Nick described Huntington disease as a hereditary neurological condition where the onset of symptoms is usually shown in people that are in their 40s and these symptoms progressively get worse until death. He also explained that HD follows an autosomal dominant pattern of inheritance meaning an affected person has a 50 percent or a one in two chance of passing the condition on to each of their children. Jane was unsure whether she wanted a test to see if she would develop the condition or not. Nick reassured her that this was fine and that she did not actually have to make a decision to proceed with testing until she was ready. 

In the following few months, Jane was angry. Why her? Why did she have to think about such an adult thing when her friends at school only had the normal high school dramas to contend with? Jane decided to go back to see Nick, but this time she took her best friend with her. She wanted to discuss things with Nick that she did not want her mother to hear. Jane was worried about her father and wanted to know what was likely to happen to him and how he would die. Nick described the different stages of the condition. Jane was only 17, but she disclosed to Nick that she wanted to have a family after becoming a pilot. Nick explained that it was possible to have children who would not have the faulty HD gene by using an IVF technique called preimplantation genetic diagnosis. 

Nick and Jane discussed the advantages and disadvantages of having predictive testing for HD. Nick said something that surprised Jane; Nick mentioned that most people who know they are at risk of HD choose not to have testing. Nick explained that some people who chose to undergo testing do so to help them plan what they would like to do with their life. Jane decided to have testing after she finished high school. She graduated and in the summer vacation she went back to see Nick for testing. She chose not to share her results with anyone. She did, however, choose not to move away to go to college but to stay at home to spend time with her dad. Jane found a job at a local travel agency where she enjoys planning vacations for herself and her clients. While I may never know what her results were, you can’t help but be proud that she took charge of her health, in her own unique way and in her own time.  

I wonder what her results are and if she will ever become a pilot. Only time will tell.  While some decide to forgo genetic tests, it could help families and people like Jane prepare for the future, whether that is starting a family or deciding on a career. 

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