Multiple sclerosis: research in British Columbia.

To the editor: In their article on multiple sclerosis (Can Med Assoc J 1982; 126: 377-382, 385) the most recent reference Warren and coworkers cite on familial predisposition to multiple sclerosis is 19 years old.' This gives the false impression that no recent work has been done in this area. I would like to report some recent studies conducted in British Columbia on the genetic aspects of multiple sclerosis. In one recent study2 pedigree data were obtained for 364 families having two or more siblings in which at least one sibling was considered to have "clinically definite" multiple sclerosis according to the Schumacher committee criteria.3 These data were tested for "goodness-of-fit" to the polygenic threshold model of inheritance. The conclusion was that a major gene could be responsible for at least a portion of the cases. Warren and coworkers found that 22 of 100 case subjects reported a family history of multiple sclerosis, although the diagnostic criteria used for relatives of patients were not specified. To date in British Columbia genetic histories are available for 638 unrelated patients with "clinically definite" multiple sclerosis 416 were ascertained as part of an earlier study4 and 222 were seen at the multiple sclerosis research clinic of the University of British Columbia. Of the 638 patients 106 (17%) reported at least one relative with "clinically definite" multiple sclerosis, and 31 (5%) had at least one relative with "possible" multiple sclerosis. Warren and coworkers reported that 14 (1.3%) of 1088 first-degree relatives (parents, siblings or children) of their patients with multiple sclerosis also had the disorder. A preliminary report5 based on data from British Columbia gave empiric recurrence risk data for first-, secondand third-degree relatives of patients: in a group of parents and siblings of 416 unrelated patients with multiple sclerosis 52 of 2005 also had the disease, for a risk of 2.6 . 0.6%. This calculation excludes children of index patients since most would still be young enough to be at risk of having multiple sclerosis develop. For this reason we are currently deriving age-specific empiric recurrence risks. Accurate prevalence data are not yet available for British Columbia, but it is estimated that the prevalence of multiple sclerosis is at least 100/100 000 population. Our findings suggest that the risk of multiple sclerosis developing is at least 26 times greater for firstdegree relatives (excluding children) of index patients than for the general population. The risk of 15 times cited by Warren and coworkers is probably low, since children of index patients were included in the calculations. I wish to stress that work on familial aspects of this disease is continuing in British Columbia and other areas.