Don't know if this has been posted before, but the link below goes to a long, dense webpage on genetics and other aspects of multiple sclerosis courtesy of the "Online Mendelian Inheritance in Man" site from Johns Hopkins. It's good bedtime reading if you're trying to get over insomnia...but a good reference anyway.
http://www.ncbi.nlm.nih.gov/entrez/disp ... ?id=126200