Dr. Kevin Most: Genetics
Historically genetic testing has been left up to doctors to order and has been quite limited in scope. We use it in newborns to test for a few genetic illnesses, in some cases it is used in pre pregnancy to see if both individuals happen to carrier a faulty gene and it is used in some other diagnostic areas we will discuss later.
You all probably heard that Steve gave his staff genetic testing from a company called 23andme . They then discussed the results and although I missed it I would bet there were some surprises and interesting results. As kids growing up we always would say we were 1/2 xxxx 1/4 xxx and 1/4 xxxxx. Most of the time this was based on a few generations and almost always incorrect. Growing up I always thought I was 1/2 Irish with my mom being irish and the other half split between German and French from my fathers side. The current DNA testing actually goes back thousands of years and it really gives historians great insight into the migration patterns. This use of genetic testing is more of a novelty and conversation piece but the power of genetics will explode over the next generation.
The direct to consumer genetic testing market is now exploding and it is going beyond simple ancestry information. 23andMe will now test for genetic mutations that may put you at a higher risk of developing specific illnesses. These include celiac disease, Parkinson’s, Alzheimer’s and some blood clotting disorders as well. Although it is approved for direct to consumers, the results should be shared with your primary care physician to really interpret the results and see what screening or lifestyle changes you may need to consider. This testing is not used to make a diagnosis but is used as information about your chance of developing one of 10 illnesses.
Currently the use of DNA testing is used in many legal cases, it has been used to prove who actually is the father of a child and it has been used in many cases to prove proof of a crime or innocence in a crime. We all have heard stories where DNA analysis has allowed a individual who was wrongly convicted to be released from prison. These uses are great for individuals but it is time we start thinking beyond novelty and single advantages.
There is an initiative that is starting that will hopefully collect the DNA of millions of Americans. Individuals will then have their medical conditions, medication effectiveness and many more points of data monitored. Eventually the data will allow doctors to treat patients with more accuracy thus increasing the quality and quantity of life. Let’s go thru a few examples, since it is spring let’s discuss allergies. We have discussed many times in the past the treatment of allergies, with pollen counts very high and going higher this week, spring allergies are hitting hard. We have discussed that Benadryl a very inexpensive antihistamine is great but for many people it makes them drowsy. Claritin, Allegra, Zyrtec are 3 non sedating antihistamines yet the effectiveness of their blocking symptoms varies from person to person. It is thought that perhaps there is a genetic component to the effectiveness of many medications. So lets say we collect all this data and we find out the Zyrtec works well for the person with a specific genetic sequence. This would allow the doctor to confidently say, for your allergies Zyrtec is the best medication for you. Now many of you may say who cares, well think about the individual with depression where the effectiveness of a medication may not be known for months, that individual may potentially suffer for close to a year before finding the correct medication to aid them in that fight.
This may be the same for high blood pressure, heart arrhythmias, arthritis…… the list goes on. Probably the most important area will be in Oncology and the treatment of Cancer. We already have genetic markers that aid physicians in treatment options. Chemotherapy is toxic and the side effects are awful, wouldn’t it be great if we could say to a patient based on your genetic make up we know that this chemo drug is the best for you and that now we know that you will only need to take it for 3 weeks compared to the past where you had to take if for 6 weeks, or we find out that radiation will not help an individual with breast cancer in some cases but is very effective in other cases.
Now we all have to realize this is not a few years away, it may not be a decade away but with this work starting some changes will be seen in our lifetime.
Currently we use genetic testing in some cancer screening, you may have heard of the BRCA genetic mutation which greatly increases a women’s chance of breast cancer. In the general public about 10-12 percent of women will develop breast cancer, that is a very high percentage and thus we do screening in the hopes to identify the cancer early and treat it at this early stage. In contrast a women who inherits the BRCA 1 genetic mutation that rate jumps to over 50%. Worse yet, ovarian cancer which does not have a screening test impacts just over 1 % of the total female population but in individuals with the BRCA mutation this jumps to close to 40%. The mutation in BRCA actually impacts the bodies ability to repair DNA damage and thus in patients with this mutation their ability to essentially fight off cancer is impacted. Again we talk about the ability of a celebrity to highlight medical information. This is the genetic mutation that Angelina Jolie has.
Current thinking is that this known mutation is the tip of the iceberg and still in elementary stages but it is setting a tone for what is possible.
We recently discussed the recent increase in patients younger than 50 developing colon cancer, may this have a genetic component? Possibly but in this case it may be more environmental than genetic yet the ability to mine large amounts of medical data may help us get more answers on this recent upsurge.
You will hear more and more about collection of genetic material for a national data base probably later this summer, hopefully many will consider joining the data base to help advance the science behind genetics and medical care.
Predictions in Medicine are often fraught with it being just a good guess. One common one is when a parent asks how tall will my child be when they are done growing. Historically physicians have used a few ways to predict. One is to double the boys height at age 2 or double a girls height at 18 months. Another popular way is to add the parents height, add 5 inches for boys or subtract 5 inches for girls and then divide by 2.
Physicians track your childs growth at each visit. They may show you a growth chart as we plot points along the curve each visit. This chart allows us to monitor and make sure your child is progressing as expected. If the child falls off the growth curve it often prompts the doctor to do some additional tests to check for hormone levels, thyroid levels, diabetes check to try to explain and correct the growth back to the expected curve.
Genetics, nutrition and environment may play some role. Growth spurts occur at different ages for different children. Accuracy on the guess is often helped with x rays that show what is happening with the growth plates.
Probably the biggest message is don’t freak out about your child’s height just make sure he is having his pediatric visits so the monitoring can be tracked. If you are concerned about your childs height talk to your doctor. They are used to the question and will go over your childs chart and expectations.