Clues to the mystery of multiple sclerosis

Abstract

While the cause of multiple sclerosis (MS) remains obscure, epidemiologic investigation suggests that environmental factors encountered years before onset could be responsible. Studies elucidating age-specific onset curves, worldwide distribution, epidemics, clustering, and risk of contraction after migration are consistent with the belief that MS may be caused by exposure to an infectious agent, possibly viral, at or shortly after puberty. Indirect evidence from serologic studies of serum and CSF shows elevated antibody titers to a number of viruses in MS patients. Although the absence of reproducible direct evidence of virus or viral remnants in brain tissue of patients with MS casts doubt on the viral hypothesis, it cannot be excluded. The theory that MS represents a complicated virus-host interaction with a secondary mechanism that initiates or prevents the process and its exacerbations implies that at least two components are present--one producing the disease and one immunizing against it. Results from studies of geographic distribution, migration, and age at onset make this model plausible. Further understanding of the molecular biology of viruses and results of epidemiologic studies of migration will help settle this argument and may lead to prevention of the disease.