Prognosis of multiple sclerosis: environmental factors.

Epidemiological data have suggested a role for environmental factors in multiple sclerosis etiology. Infectious diseases, exposure to toxins, immunizations, nutritional and hormonal variables, and trauma are the most studied and biologically plausible risk factors for MS. Their putative role in determining or simply triggering MS development in genetically prone subjects suggests a possible involvement of the same factors in modulating the subsequent behavior of the disease and its prognosis.