Clinical features, disease course and prognosis in patients with paediatric and young adult onset multiple sclerosis

Background. Multiple sclerosis (MS) patients develop their first symptoms before adolescence approximately in 5%. Studies comparing clinical and prognostic characteristics in early onset MS, did not show homogeneous results. Objective. Aim of this study was to investigate characteristics of early onset MS patients and compare them with patients who experienced MS onset later. Methods. MS patients diagnosed as affected by MS according to Poser's criteria, were included if they experienced symptoms onset before age 25. They were classified in three groups. Group A: patients who had their onset until they were 16 years old Group B: individuals with onset between 17 and 20 yearsGroup C: patients with onset between 21 and 25 years of age. Clinical characteristics of the three groups were compared. We analyzed the following variables: sex ratio, mono vs. polysymptomatic onset, functional system involved at onset, proportion of relapsing patients, frequency of relapses, proportion of patients with positive oligoclonal bands (OCB), EDSS score at the end of follow-up (June 30th, 2012), frequency of patients who reached an EDSS of at least 6, differences in time to reach EDSS 6, time elapsed from disease onset to secondary progressive phase (SP). Results. We included 522 MS patients (group A: 74, group B: 162, group C: 290). Sex ratio varied from 1.55:1 in the first group, to 2.24 and 1.99 in the second and third respectively. Only 8 individuals (1.5%) had a primary progressive course. Polysymptomatic onset occurred in 16.2 and 17.9 % of group A and B, compared to the 11% of the patients in group C (p=0.04 for the comparison between group A and group C). We did not observe significant differences in the rates of patients positive for OCB in the three groups (85% group A, 74.1% group B, 77.1% group C). There were no significant differences between the frequency distribution of the three groups regarding EDSS score of at least 6. Mean time to reach the EDSS score of 6 was significantly longer in younger patients compared to the others (group A: 25 years, group B: 20 years, group C: 15 years; p= 0.003). This time was significantly longer in women in each of the three groups of age (p= 0.02). We observed a significant trend in time to reach the SP phase associated to the increase of age (p= 0.03). Conclusion. This study confirms that clinical characteristics vary according to age at onset also in MS, suggesting that pathogenic mechanisms of the disease may be influenced by factors modified by age.