SMA

This is a pretty good overview of how SMA is inherited. The last paragraph describes what SMA does to the human body. It's really hard to believe that this is what I have with no family history. Both of my parents need to be carriers.

Source: http://www.fsma.org/exp_answer_19.shtml

Question: What are the dominant and recessive traits of SMA? How does someone get it?

Answer: Dominant and recessive traits are specific terms used to describe different genetic disorders and refer to the way that a genetic disease is passed on from one generation to the next or inherited.

How are traits inherited? Each cell in our body contains a nucleus that houses DNA on structures that we call chromosomes. Each chromosome comes in two copies, one copy was passed down from our Dad (from the sperm cell) and one copy is passed down from our Mom (from the egg cell). This means that we have two chromosomes 1, 2, 3 etc. Genes, which are contained on our chromosomes, code for all the material (proteins) in a cell that tells it what to do. In general, we have two normal copies of each gene (one inherited from each of our parents). This basic information will help me explain the difference between a dominant and a recessive trait. For some genes, we absolutely need the two copies to be functional. For other genes, we are OK even if only one copy is functional. Mutations are changes in DNA that renders a gene semi-functional or completely non-functional. A dominant trait is one where we need both genes to be functional. For example, Amyotrophic Lateral Sclerosis (ALS) is an autosomal dominant trait. Individuals with ALS have one normal ALS gene and one ALS gene that has a mutation. Thus, all individuals that have a mutation in the ALS gene will most likely, at some point in their lives, display the symptoms associated with ALS even though they have one normal gene.

Childhood-onset SMA is a recessive trait. SMA is caused by mutations in a gene that is called SMN (for survival motor neuron gene). We only need one normal SMN gene for our motor neurons to develop and function normally. Individuals with SMA have two mutant SMN genes because they inherited one mutant gene from each of their parents. Because their parents each had one normal and one mutant SMN gene (they were carriers), they did not have SMA because one copy of SMN is sufficient. Thus SMA is a recessive tait, the fact that we have a SMN mutation stays hidden (recessive) until we produce a child that inherited the SMN mutation from each of his/her biological parents. So SMA is an inherited disease that is passed on from parent to child through their SMN gene. Both parents have to be carriers, that is, have one normal and one mutant SMN gene. In a recessive trait, carriers are asymptomatic (do not have any SMA symptoms). About 1 in 50 individuals are SMA carriers. This means that (in terms of probabilities) in about 1 in 2,500 couples, both would be SMA carriers. Each time two carriers have a baby, there is a 25% chance that the baby inherited both SMN mutations and will have SMA, 50% chance that the baby will be a carrier, and 25% chance that the baby inherited both normal SMN genes. Thus, for a recessive trait, each time that two carriers produce a child, there is a 1 in 4 chance that the baby will have the genetic disease in question.

SMA stands from spinal muscular atrophy. Because SMN is very important for normal functioning of motor neuron cells in the spinal cord, when SMN is almost completely absent, spinal cord motor neuron cells die. When these cells die, they stop sending messages to the muscles they are responsible for. Motor neurons are the batteries of muscle and tell muscle when to move and when to rest. Because the muscle is no longer receiving these messages, it wastes away or atrophies. I hope that this answers your questions.

Louise R. Simard, Ph.D.
Associate Professor
Centre de Recherche de l'Hôpital Sainte-Justine
January 2005

11

I saw my doctor this morning. He reviewed the blood test results from last week and everything looks fine. The neurologist who did the EMG testing on me a few weeks back wrote a long report on me and he showed me some of the things she wrote. She believes that I have Spinal Muscular Atrophy Type III. Normally, it's supposed to affect people in their late teens and early twenties and she thinks I've had it for a long time without noticing it. It will be three weeks tomorrow since I gave a blood sample for the genetic test, and still no result. My doctor has dealt with a few cases of ALS (which share some muscle weakness symptoms), but he's only seen this in a textbook before.

I will be seeing a physiotherapist on Friday. Hopefully, there are some exercises I can do that will help.

Also, I finally figured out yesterday how to get to my classroom at VCC from the Pender St entrance without going up any stairs. It takes a long time, but it can be done. I fell down getting off the trolley bus when I went home last night. The bus driver had to help me get back up. I'm looking forward to seeing those new low-floor trolley buses go into service.

Jer is now all moved in. I think he has watched more TV at my place in the last few days than I have in the 6 months I've been living there.

10

I have a roommate. Jer is going to stay at my place for a few weeks. My parents have a futon mattress that they use to have guests over, and they dropped it off tonight. I still need to work out some logistics, like finding a place for Jer to park his car, but hopefully everything will work itself out.

9

Yay! More blood tests! I hate needles. The GP I saw yesterday just moved here from Port Alberni and has been practicing for 9 years. He seems good. He ordered a chest X-ray and abdomen ultrasound because of the weight loss and also some more blood tests. I did the X-ray today, but the ultrasound won't be for 2 weeks.

The neurologist I saw today took my information and did the same examination all the others did. He thinks it's a myopathy or atrophy and that it's genetic. Both my parents have to be dormant carriers of the genes in order for that to be true. I asked him to just schedule a biopsy without waiting for the genetic blood test results. If it ends up conclusive then we can always cancel it. Otherwise that's another week of waiting since I'll be further back in the queue to get the biopsy done. Whatever I have, it's rare.

He is going to refer me to a physiotherapist who can hook me up with some exercises to tone my muscles. Any other exercises could make things worse.

8

I just weighed myself. My normal weight is 165-170 lbs. I'm at 141.6. That's 25 pounds under my normal weight. I know I've lost weight, because I've been wearing my belt at 4 notches instead of 2 for the last month (about a 2" loss on my waist). I never thought that it was that much. A friend also commented that I'm looking really skinny.

I am seeing a GP tomorrow afternoon. I'll definitely bring this up. I have lots of questions.

7

I had my parents over at my place for dinner tonight. They are so worried about me and want to spend time with me, so I invited them to my place. To get to my apartment after work, I got off the bus and then turned into the lane to walk over to the entrance with no stairs. I missed my footing a few feet into the lane on a pothole and went down. Since there was no way I could get up on my own, I called out to the first person who walked past and asked for a hand getting up. The first person was this black dude who came over and offered his hand to help me up. I don't have the strength in my legs to get up with just a hand for support and he had to pull my body up.

As coincidence would have it, my parents drove into the lane right as he was lifting me up. They stopped right away and jumped out of their van. By then I was standing and stable but they ran to me and my dad grabbed me. The guy took off and I didn't get a chance to thank him. I think they scared him away, rushing over so fast. My mother later told me she thought I was in a fight with him. That's ridiculous. I called out a thank you but I'm not sure he heard me. That really sucks, and I feel bad, because most people are conditioned to say "no" whenever approached on the street, and this guy helped me out right away.

It's really easy to imagine right now how hard it would be for someone in a wheelchair to get around. I notice the little things like the sidewalk ramp depressions on the street crossings for people to wheel themselves up on.. things that are just taken for granted. On the flip side, I also notice how relatively easy it is to get around; elevators are everywhere, and there are ramps almost everywhere that there are stairs. Twenty years ago that wouldn't have been the case, but it still doesn't make it easy. I'm taking a longer route to walk to work from the bus stop in the morning, but there is less chance I will fall down.

Last week I was really depressed from going to see a bunch of doctors and not knowing what was happening to me. Thursday and Friday really lifted me up, as did Sunday. I was really depressed on Thursday and didn't even bother going to work after finishing with the neurologist. I went to the opera on Thursday night and even though it's not my thing, I'm very glad I was able to spend time with some close friends. I would go again just for that. On Friday, I went out to the Caprice and even though I sat for most of the night, I still went up and danced a bit, holding one of the girls' hands to keep stable. Besides.. someone had to watch the alcohol while everyone was up dancing. I also now know that it takes two Heinekens for Mike to go up on the dance floor. On Sunday, a new friend I met about a month ago called me up in the afternoon because she had thought of me and had bought an herbal treatment that she thought might help. She wasn't home when I picked it up but had left a card with it. That card is now in my living room next to my photos.

I will do something special for everyone close to me. I just need to think of what to do.