This longitudinal study from the University of British Columbia examined the clinical course of early-onset MS (EONS), defined as disease onset before age 16, in 116 patients tracked for an average of 19.76 years. Early-onset MS represented only 2.6% of MS cases as primary progressive, with 53.1% eventually developing secondary progressive MS. The median time to secondary progressive conversion was 23 years after disease onset, with patients typically reaching permanent disability milestones (Expanded Disability Status Scale scores of 3.0 and 6.0) at mean ages of 28 and 32 years respectively.
The annual relapse rate in early-onset MS was 0.54 per year, comparable to adult-onset MS, yet the progression to disability occurred at younger absolute ages due to disease onset in childhood. Importantly, early relapses were associated with disease course phenotype—patients with more relapses in the first disease year were more likely to develop secondary progressive MS. This finding suggests that initial disease activity patterns may predict long-term progression, potentially allowing identification of higher-risk patients who might benefit from more aggressive early treatment.
These results have important implications for pediatric MS management. Early-onset MS carries the same risk for progressive disability as adult-onset disease, but developing such disability in young adulthood imposes extraordinary life consequences (education, career, family planning, social development). The association between early disease activity and later progression emphasizes the importance of aggressive disease modification in pediatric MS to prevent early secondary progressive conversion. For families and healthcare providers managing EONS, these longitudinal data underscore why early, intensive disease-modifying therapy may be particularly important to preserve long-term function during critical developmental decades.
