Disease gene clustered on chromosomes - Is there any truth to this? (Jun/08/2006 )

At one point there was the theory that genes for the same disease or similar diseases may be clustered on the same chromosome. I suppose the theory was that they may somehow be regulated together. Is there any truth to this theory? I'm wondering because I'm studying a gene that is predicted to be involved in a certain disease. There are other genes nearby on the same chromosome that are known to cause that disease. Is it a far stretch to make the statement that due to this "close" proximity that this gene may be involved in the same disease? I know, grabbing at straws. Hey, I'm writing my thesis, what do you expect? Of course, if you have any sort of reference to this clustering besides just general handwaving that would help me out greatly.

Look at autoimmune diseases. Generally their associated genes cluster on the short arm of chromosome 6 in the MHC region. Although of course there are usually othere genes associated with them as they are complex diseaes. It is not inconceivable to have genes which do similar functions be clustered together. Therefore, it is not inconceivable to have several genes predispose to the same disease.

Another thought...how do you know that your gene isn't in linkage to the other genes that cause that disease?