Objective: The impact of relapses on the disease course of relapsing MS remains to be determined. This study aims to identify and characterize clinical phenotypes of relapse onset MS in a longitudinally studied cohort.

Methods: We recorded the clinical course of MS during the first decade of disease, using five-year epochs. Patients were stratified as: no worsening due to relapse or secondary progression (type A), relapse with worsening seen without secondary progression (type B), secondary progression with no worsening due to relapse (type C), worsening due to relapses mixed with secondary progression (type D).

Results: Of 176 patients followed from diagnosis for 12.62 ± 4.18 years, 93.2% (164/176) had increased disability in their first 5-year epoch of MS and 52.2% (72/138) in the next. The phenotypes significantly differed by EDSS change during each epoch (p<0.001), final confirmed MSSS (p ≤ 0.002) and relapse rate (p<0.001). Type D fared worse than others by change in EDSS and MSSS.

Conclusions: We identified multiple specific phenotypes of MS and temporal shifts between phenotypes according to relapse type and progression.