It was a few months ago when I felt as though I couldn’t lift the weight of my head, and I had trouble walking because my legs felt so weak. I decided to make my way to a hospital. I waited for hours until I finally got to see a doctor. In the few seconds I saw him, he prescribed me some medications and then sent me on my way. It wasn’t until a couple weeks later that I realized I was losing my hearing. At that point I knew something was definitely wrong, so I decided to go back.
The doctors decided to dig deeper and run some more thorough tests. Based on my symptoms, they began to consider mitochondrial diseases. They performed a DNA test on my mom, my dad and I. I sat with my fist closed tightly as they located the popping vein in my arm and stuck a tiny needle in it. The purpose of this test is to determine whether or not there are any mutations present in the mitochondria’s DNA sequence. They also performed a biochemical test, which required a biopsy and they took a sample of my liver. This test let them know if my mitochondria, the most important organelle in aerobic cellular respiration, is working properly and effectively at the rate it should be. These tests assess mitochondrial function and duplication, while looking for any mutations in the sequence of my DNA.
They sent me home with no new knowledge, except for the fact that the test results may take up to 6 weeks. Thankfully, they came in two weeks early. At this point I felt weaker than ever before. My thought process had slowed, as I constantly delayed answering people when I was asked questions and I’d been vomiting almost every second day. I went back to the hospital, and they placed me in one of the beds. I looked to my right and saw a little kid getting his arm casted. He must’ve taken a hard fall during recess. After 30 minutes, the doctor finally came in and he started talking all his medical jargon which I couldn’t understand. All I want is for Dr. Hayword to speak a language I was able to comprehend.
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| Figure 1: Composition of mitochondria demonstrating the locations of the DNA present in the structure and how it is throughout the entire structure. |
“What we believe you have falls under the category of disorders where there is a drop in mitochondrial DNA which has a great effect on many tissues throughout the body. This DNA, which is present throughout the entire mitochondria, is important in maintaining its structure, since it is where cellular respiration and energy production takes place in every human cell. (refer to figure 1) When there is a mutation in the DNA sequence, it isn’t harmful at first, but over time, the DNA duplicates and the mutations will accumulate, causing your symptoms.” explained Dr. Hayword. He continued with his medical talk while I sat in bed with a confused look on my face. “This disease causes mutation in the TK2 gene which causes TK2-MDS. TK2 Mitochondrial DNA Depletion Syndrome. This gene is responsible for providing instruction for the production of thymidine kinase 2, an enzyme whose task is to produce and maintain mitochondrial DNA. It allows the recycling of nucleotides, the building blocks of DNA, which can fix errors in the DNA sequence. When there are mutations in the TK2 gene, it reduces thymidine kinase 2 activity, which means there are less nucleotides to repair DNA.” I was still sitting there trying to understand how this could happen to me. Of all people, why me?
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| Figure 2: Demonstrates the way mutations pass on to the next generation. In this case, the picture to the very right is representative of this situation because the child received both recessive genes. |
“The reason I ordered tests for mom and dad as well is because this is an autosomal recessive pattern of inheritance. This means the mitochondrial disease is a result of both parents having the specific mutated gene and both of these genes being passed on to the child. (refer to figure 2) Looking at the test results, both of you have the mutated gene. There was a 25% chance of your child receiving both recessive genes, and looking at her tests, both were inherited. This is a very rare disease as only 16 people in the world have had it. It is normally more fatal in babies and children, but you’ve managed to go through most of your teenage years with it, which is a good sign.”
All that was going through my head was “please let there be a cure… please let there be a cure”. To my luck, there is no cure, but there are treatments. I asked Dr. Hayword what he believes is the best approach and he suggested Nucleoside bypass therapy. The goal of this treatment is to restore the nucleosides until there are enough again. This is an oral treatment, taken in the form of a pill. These nucleosides would allow for the repair of mutations in DNA sequences. The only downfall is that this treatment was only available in the United States which means OHIP doesn’t cover the costs and my parents had to spend about $23 400 in one year for my treatment. Although it may have been expensive, it was all worth it in the end.
Here I am, at the age of 17, still alive and I feel stronger and stronger each day. I’ve still got a while to go in the hospital but it’s alright because I’ve already become friends with my roommate and every now and then in the hospital, the nurses and I have a few wheelchair races down the halls. Today, with the help of CHEO staff, we were able to have a bake sale in the main lobby and we raised approximately $500 which will be sent to the University of Calgary, as they have the infrastructure to investigate the role of mitochondrial DNA and dynamics in disease. Although $500 doesn’t compare to the $250 000, they received from the Canadian government, I hope to one day be able to say, I helped find the answer to curing Mitochondrial DNA Depletion.
