It's All In The Genes
I took a Genetics class in college many years ago. Despite this, the knowledge I walked away with was only enough to answer relevant questions on Jeopardy... sometimes. I do remember what DNA or Deoxyribonucleic acid was. I also learned a gene was a portion of the DNA, which determines specific traits like eye color. Therefore, I knew that both my husband’s and my blue-eyed recessive trait would result in blue-eyed children.
I didn’t really care about genetics during college, besides of course ensuring I passed the class. I didn’t give it a second thought until 2016 when I was diagnosed with two cancers - a rare progressive blood cancer and breast cancer. Both cancers, as I found out, were likely caused by a gene mutation. I thought it was strange someone like myself who was relatively healthy (at least at the time), could wind up with two cancers. I also wondered if there was a correlation between both.
My oncologist recommended genetic testing when I was first diagnosed with breast cancer. I was pleased when the results showed I was negative for the most common breast cancer gene mutations, BRAC1 & BRAC2. However, the test identified I did have something called a CHEK2 mutation. I had never heard of it before so I looked it up. I saw there was approximately a 50% risk of getting breast cancer. This hereditary gene mutation also has the potential to cause a whole slew of other cancers.
Learning about JAK2
After a routine lab test showed my blood levels were all elevated, the hematologist tested me for a gene mutation called JAK2 V617F. The test was positive. The JAK2 mutation was first discovered in 2005. This mutation has a clear link to a classification of blood cancers called myeloproliferative neoplasms (MPNs), especially PV. Therefore, I was back to researching, wishing I had paid more attention in my Genetics class.
My searching revealed 95% to 98% of individuals diagnosed with PV have the JAK2 mutation. The JAK2 causes a malfunction, which results in the overproducing or proliferation of blood cells. The over-production of red blood cells causes a multitude of issues like blood clots, heart attack, and stroke, along with a plethora of miserable symptoms.
Even though the JAK2 mutation was the PV culprit, how did I get the mutation to begin with? I discussed this in-depth in one of my earlier stories called Medical Mystery Tour. One of the things I wondered was if there a hereditary link? At the time, I could not find anything significant. When I inquired about how I got the JAK2 mutation with hematologists and other specialists, I mostly heard “genes mutate as we get older.” This was perplexing for me. I was in my early 50s at the time. I wasn't that old!
A couple of interesting presentations came out of the 2020 American Society of Hematologists (ASH) Meeting about MPNs and the JAK2 mutation. One study determined the JAK2 mutation could occur as early as before or shortly after birth. Despite the early mutation onset, however, it can be decades before there are any disease symptoms. This was exciting information; there was a study to negate the “old gene mutation” theory.1
Research shows there is a prevalence of JAK2 in people with normal blood counts that never develop an MPN, so it makes me wonder why I was one of the “lucky” ones that actually developed PV. Another study discusses the possibility that other genetic risk genes such as the CHEK2 could potentially have an effect on cancer development. Although somewhat technical and beyond my genetics background, I interpret it to mean that my CHEK2 mutation may have somehow had an impact on my development of PV.2
Although this is all very interesting information, it is preliminary and more research is needed.
Until then, perhaps I should pull out my college Genetics textbook (which I actually still have) and brush up on genetics.
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