Scientists have found that a single change in a person’s genetic material can cause primary progressive MS. They say this finding could lead to a cure for a disease that cripples millions of people. Researchers have long suspected that multiple sclerosis resulted from some kind of interaction among genes. Individuals with that genetic interaction, they thought, were more likely than others to get sick. They also believed that something in the environment, such as a viral infection or lack of vitamins in the diet, could activate the disease. But Canadian researchers have found that is not the cause of the most severe form of multiple sclerosis. With primary progressive MS, a single mutated gene can greatly increase the risk for developing the disease. This single gene is called NR1H3. The Canadian researchers are with the University of British Columbia in Vancouver. They reported the findings in the journal Neuron. The researchers examined medical records for 2,000 Canadian families with family members who had MS.