Multiple Sclerosis in Twins and Their Relatives: Final Report

THE RELATIVE roles of genetic and environmental influences in the etiology of multiple sclerosis have not yet been assessed with certainty. The well established familial tendency of the disease, which can scarcely be explained away by such theories as that of "common exposure", 1 implies that a genetic factor might be important. On the other hand, environmental factors are suggested by the unique epidemiologic features of the disease, the evidence for an immune reaction (frequent elevation of γ-globulin in the cerebrospinal fluid [CSF]) and, perhaps, the tendency in many cases to remissions and recurrences. Ten years ago we studied a number of twins, one or both of whom had multiple sclerosis, and their relatives to determine whether genetic factors of appreciable magnitude could be demonstrated. 2,3 The results of the first study were consistent with a hypothesis of autosomal recessive inheritance with reduced penetrance, but the evidence was not