Genetic Predisposition vs. Disease Acquisition
Posted September 17, 2007 by Dr. T.R. Morris
Many patients ask me: Does having a gene that predisposes you for a particular disease mean that you will get the disease? The simple answer is no, having a risk factor does not mean that you have a particular disease or that you will necessarily develop it.
To illustrate this point, this summer scientists published studies which showed that genetic variations of the IL-2 and IL-7 receptors each add about 20-30% chance to an individual’s risk of developing the nerve demyelinization disease Multiple Sclerosis (MS). While these numbers may seem impressive, it is important to note that the incidence of MS in the Northern United States is about 30 cases per 100,000 and so a 30% increased risk is not by itself jaw-dropping from a public health standpoint.
The new research about the interleukin receptors link to MS was a BIG breakthrough though. These were the first genetic links to MS found since 1972, when researchers discovered that having a variation in the HLA-DR which raises the risk of developing MS nearly six fold.
The million dollar question then becomes: Why do some people with these three genetic risk factors get MS while others with the same genetic risk facts do not? First, I’d say that we are a long ways off from knowing all the genetic risk factors for MS and even further from understanding the interactions between these genes. Genetics aside, my guess is that investigations into psychoneuroimmunology, environmental exposures and other lifestyle factors will fill in many of the blanks left behind by the genetic links.
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