Multiple sclerosis (MS) is a “chronic inflammatory autoimmune disease of the central nervous system (CNS),”1 characterized by demyelination and axonal loss.2 Although the elements that initiate this inflammatory response are not understood, an autoimmune response directed against CNS antigens is suspected.3 Different patients may have different inflammatory etiologies. For example, some patients appear to have T-cell mediated or a combination of T-cell and antibody-mediated autoimmune responses.3 Others have a primary disorder within the myelin-producing oligodendrocyte cells, reminiscent of virus- or toxin-induced demyelination rather than autoimmunity.3

MS consists of four subtypes, each with a different clinical course: relapsing-remitting multiple sclerosis (RRMS), secondary progressive MS (SPMS), which typically starts out as RRMS, primary progressive MS (PPMS), and progressive relapsing multiple sclerosis (PRMS). (Table 1)

Risk Factors for MS

The etiology of MS is multifactorial and appears attributable to the combination of genetic predisposition and environmental factors, including exposure to Epstein-Barr virus (EBV), cigarette smoking, reduced vitamin D levels, elevated body mass index (BMI), and poor diet.2 These risk factors appear to act synergistically, multiplying the risk of MS in individuals exposed to more than one.4 Given the differences in disease course and prognosis of the various MS subtypes, it may be possible that these risk factors exert different effects on each subtype.3