Genetic risk factors in multiple sclerosis and approaches to their identification.

Development of multiple sclerosis (MS) is believed to involve genetic as well as environmental factors. A complicating aspect to the study of aetiological factors in MS concerns the possible existence of genetically different subtypes of the disease. In addition, a relatively large number of susceptibility genes could be involved. Most likely, the contribution of the single genes to the susceptibility to MS is modest. However, interactions between different genes could result in a dramatic increase in disease susceptibility (synergistic gene effects). In this short review we focus upon genetic heterogeneity and gene interactions in MS. We also outline approaches to the genetic analysis of complex disease traits such as MS.