The familial nature of multiple sclerosis: empiric recurrence risks for first, second-, and third-degree relatives of patients.

Although the risks are low, relatives of multiple sclerosis (MS) patients have a greater risk of developing the disease than the general population. Since this is true of second- and third-degree relatives as well as first-degree relatives, the increased risk cannot be explained solely by environmental factors. This observation is part of the evidence that the etiology of MS may have a genetic component. Genetic counseling is recommended for MS patients. Empiric recurrence risks have been derived and give the counselor necessary information with which to provide this service.