Early onset multiple sclerosis: a longitudinal study.

Objective: To evaluate the clinical course of MS in individuals with onset of MS before age 16.

Methods: Patients with onset of MS before age 16 (n = 116) with complete clinical information on the clinical course from the MS Clinic at The University of British Columbia (UBC) Site Hospital computerized database (MS-COSTAR) were included in this study. The data were compared to those from the Canadian natural history study for MS clinic attendees, regardless of age at onset.

Results: The mean duration of observation was 19.76 +/- 0.90 years; the mean age at MS onset was 12.73 +/- 0.25 years. Only three cases (2.6%) had a primary progressive (PP) MS course. To date, 60 (53.1%) of 113 subjects have developed secondary progressive (SP) MS. The 50% probability for SPMS was reached 23 years after onset. For patients with relapsing remitting (RR) or SPMS the mean disease duration from onset to the time of confirmed Expanded Disability Status Scale (EDSS) 3.0 was 16.03 +/- 1.17 years (at mean age 28.47 +/- 1.14); mean duration from onset to the time of EDSS 6.0 was 19.39 +/- 1.43 years (at mean age 32.32 +/- 1.44). Annual relapse rate was 0.54 +/- 0.05 per year. The correlation between the number of relapses during the first year of disease and the course of the disease was also significant.

Conclusions: The prevalence of early onset MS (3.6%) in our study confirms the previous findings on early onset MS. A RR course was seen in the majority of cases of early onset MS. A high frequency of relapses, early age at permanent disability, and the presence of malignant cases raise the question of possible early use of disease-modifying therapy in patients with early onset MS.