Disease activity impacts disability progression in primary progressive multiple sclerosis

Background Although solid information on the natural history of primary progressive multiple sclerosis (PPMS) is available, evidence regarding impact of disease activity on PPMS progression remains controversial. Objective To describe the clinical characteristics, presence or absence of MRI activity, and natural history of a PPMS cohort from two referral centers in Argentina and assess whether clinical and/or radiological disease activity correlated with disability worsening. Methods Retrospective study conducted at two MS clinics in Buenos Aires, Argentina, through comparative analysis of patients with and without evidence of disease activity. Results Clinical and/or radiologic activity was presented in 56 (31%) of 178 patients. When stratified by age at onset, we found that for every 10 years of increase in age at onset, risk of reaching EDSS scores of 4 and 6 increased by 26% and 31%, respectively (EDSS 4: HR 1.26, CI 95%: 1.06–1.50; EDSS 6: HR 1.31, CI 95%: 1.06–1.62). Patients who presented clinical exacerbations reached EDSS scores of 6, 7 and 8 faster than those without associated exacerbations (p = 0.009, p = 0.016 and p = 0.001, respectively). Likewise, patients who presented gadolinium-enhancing lesions during the course of disease reached EDSS scores of 7 earlier (p = 0.002). Conclusion Older age at onset and presence of clinical and/or radiological disease activity correlated with accelerated disability progression in this cohort of PPMS patients.