Multiple sclerosis results from damage to the myelin sheath, which covers the axon of the neuron. The myelin sheath is made up from two types of glial cells. The University of Washington explains that oligodendroglial cells make up the myelin sheath in the central nervous system (brain and spinal cord), and the Schwann cells make up the myelin in the peripheral nervous system (nerves in the rest of the body). When the myelin sheath is damaged, the brain cannot properly communicate with the rest of the body.
Arthur Schoenstadt, MD, author of the eMedTV article “Multiple Sclerosis Statistics,” notes that between 250,000 and 350,000 people in the United States have multiple sclerosis, with women being affected twice as often as men. But what causes multiple sclerosis? MedlinePlus, a service of the United States National Library of Medicine and the National Institutes of Health, points out that the exact cause is unknown, though genetics and environmental factors have been studied.
Genetics
A new study published in Nature Genetics found that a variant of the CBLB gene may cause multiple sclerosis. With the normal gene, it moderates the immune response. But with the abnormal gene, the immune cells attack the healthy cells, as in multiple sclerosis. HealthDay News reports that the researchers analyzed the genes of multiple sclerosis patients in Sardinia, where a large number of autoimmune disorders have been identified. Besides finding the correlation between the variant of the CBLB gene and multiple sclerosis, the researchers also found six other genes associated with multiple sclerosis, which were identified in other studies on the genetics of multiple sclerosis.
Environment
But genetics are not the only factor with multiple sclerosis, as indicated with twin studies in which only one twin has the disorder. Another multiple sclerosis study published in Nature notes that with identical twins, if one twin has multiple sclerosis, the second twin also has multiple sclerosis in 30 to 40 percent of cases. HealthDay News points out in the study that the researchers did not find any genetic differences in the twins they used in the study, leading them to believe that environmental factors play a role in the onset of multiple sclerosis. Other environmental factors may protect the other twin from developing multiple sclerosis. However, they did not uncover the specific environmental factor or factors.
While these studies offer new insight into the causes of multiple sclerosis, more research is need to pinpoint exactly what triggers the disorder.