Myelin injury precedes axonal injury and symptomatic onset in multiple sclerosis.

The timing of the biological onset of multiple sclerosis (MS) is unclear. We used high-throughput discovery proteomics and samples from presymptomatic patients with MS and matched healthy controls to define the biological neurological onset and characterize the mechanisms involved. Remarkably, evidence of myelin injury was seen ~7 years before the symptomatic onset and preceded evidence of axonal injury by ~1 year. By contrast, astrocyte involvement became evident only at clinical onset. Numerous changes in the serum proteome indicate the involvement of interleukin 3 and nuclear factor kappa B pathways during the presymptomatic stage. Furthermore, people with MS with a previously reported distinct autoantibody signature showed increased immune cell activity compared to those without. We propose a protein biomarker panel that may help distinguish presymptomatic patients with MS from healthy controls, pending validation in future studies. Our findings can help understand the pathophysiology of MS as well as the cascade of central nervous system injury and might facilitate early detection of MS in high-risk people.