Heterogeneity of multiple sclerosis pathogenesis: implications for diagnosis and therapy.

Multiple sclerosis is a chronic inflammatory disease of the nervous system in which a T-cell-mediated inflammatory process is associated with destruction of myelin sheaths. Although demyelination is the primary event, axons are also destroyed in the lesions, and the loss of axons correlates with permanent functional deficit. Here, we discuss evidence that demyelination and axonal destruction follow different pathogenetic pathways in subgroups of patients. This might, at least in part, explain the heterogeneity in genetic susceptibility, clinical presentation and response to treatment observed between individuals.