[Familial predisposition to multiple sclerosis].

Seven families were studied to evaluate the influence of genetic factors in MS and its transmissibility. The disease was associated with some B7 and/or DR2 alleles in relation to the susceptibility gene in all but one case. This association was always transmissible conjointly. The carrier haplotype conditions disease manifestations and its prognosis, favorable in this series, but it is not sufficient to promote the onset of the disease. This requires a triggering factor with sometimes disorders affecting 3 generations as demonstrated by the analysis of one family. Therefore there is not a genic heredity but a predisposition heredity. Possible associations of MS with other morbid states such as insulin-dependent diabetes must be considered when counselling families.