Thanks for responding. Since there are no specific genes that have been found consistently linked to either RA or MS, we can not say for sure how your relatives' MS or RA originated. However, since there is a female predominance in both of the diseases, it suggests the possiblility that the X chromosome is involved. It may not be specific gene mutations (genetics) but rather how the genes are packaged (epigenetics). Some stress event at the cell level (ex. virus or hormones)could disrupt the proper packaging so that the underlying genes are expressed at abnormal rates (more or less than normal). That is part of the hypothesis I have been developing. I have an article in press explaining my hypothesis in more detail, and the genes I believe are involved. The article should be appearing online any day now at Medical Hypotheses. It is too complicated to explain in brief. I may be wrong but I think it is an area that needs to be considered further. Again, it is my belief that the diseases share a similar mechanism, a mechanism occurring primarily in non-immune cells with consequences that differ in RA, MS, lupus, etc. based on the vulnerabilities of the cell types in which the mechanism occurs.