Consanguinity and multiple sclerosis in Orkney.

For all patients with multiple sclerosis in Orkney who were alive in 1974 or who had died during 1958 to 1974, pedigree data were analysed. The relationship between their parents, expressed by kinship coefficients, was compared with that between parents of matched controls. The closer relationship between parents of patients suggests that it is the genes that are shared by a patient's parents, and that he inherits from both, that influence his susceptibility to multiple sclerosis.