Since I was first diagnosed with Multiple Sclerosis six years ago, I've probably been asked a thousand times, "What causes MS?" Seems like a pretty simple question, but the unfortunate truth is that nobody knows the root cause of Multiple Sclerosis. As with cancer, diabetes, and a host of other diseases, decades of research have allowed our best medical minds to only make educated guesses as to the genesis of the MS. Over the last 20 or so years, the prevailing hypothesis has been the "autoimmune" theory, which states that a patient's immune system for some reason goes haywire, and starts attacking their own cells. I often get the sneaking suspicion that diseases whose cause stumps our scientists are often labeled autoimmune, simply for lack of a better theory. Modern science isn't comfortable saying "I don't know", and when I see the word "autoimmune", I often put the words "I Don't Know" in its place. Multiple Sclerosis is an "I Don't Know" disease.
Through the years, I've come to look at the MS disease process as kind of resembling an automobile engine. In order to start a car engine, you must have gasoline in the tank, oil in the pan, and a key for the ignition. If one or two of these elements are missing, the car just won't start. In much the same way, MS requires a number of elements to be present for it to take hold of a patient's physiology. There is solid evidence that bacterial or viral infections play some part in the disease. Likely culprits include Epstein-Barr virus, Chlamydia Pneumonia, Varicella Zoster, and the Human Herpes Viruses. Many of these bugs infect large proportions of the population; for example, EBV is present in at least 85% of adult Americans. Obviously, only a tiny proportion of them develop MS, so EBV alone can't be the cause of the disease. There is also strong evidence that environmental toxins play a role in starting the MS disease process. Again, though, the vast majority of people exposed to common environmental toxins don't come down with MS. Therefore, there must be another component required for MS to take hold, most likely a genetic susceptibility.
It's been theorized that some people carry within their DNA remnants of ancient retroviruses that have over the eons incorporated themselves into the human genome. This retroviral DNA is normally inactive and completely benign, but perhaps the presence of a combination of infections and/or toxins can activate this DNA, and thus cause a person's immune system to see their own cells as harmful invaders.
So, to get back to the engine analogy, for a patient to get MS, they must have gas in the tank (a chronic viral or bacterial infection), oil in the pan (exposure to another environmental toxin or infectious agent), and a key to the ignition (a genetic predisposition to the disease). Without the right combination of elements present, even a person genetically susceptible to MS might never get the disease. Likewise, without genetic susceptibility, a person might be exposed to any number of MS triggers, and never develop Multiple Sclerosis. In my opinion, it's an unfortunate synchronicity of seemingly unrelated elements that turns the key that starts the MS disease engine. These elements may differ from patient to patient, and these differences in triggering elements might account for the vastly different ways that MS can present itself from case to case.
So, gentlemen (and women), start your engines. Or better yet, don't...