Truly benign multiple sclerosis is rare: let's stop fooling ourselves--yes.

MULTIPLE SCLEROSIS MSJ JOURNAL Multiple sclerosis (MS) affects young adults during the most productive period of life. 1 The disease course is highly heterogeneous and includes a subgroup of patients who show little or no disease progression and minimal disability decades after the clinical onset, the so-called benign MS (BMS). 2 In a 1996 consensus meeting, BMS was defined as a 'disease in which the patient remains fully functional in all neurological systems 15 years after disease onset'. 2 However, in the literature, the definition of BMS has been mainly focused on the preservation of motor abilities of the patients, usually relying on the Expanded Disability Status Scale (EDSS) that is particularly influenced by ambulation and lacks sufficient association with important manifestations of MS, such as inability to perform daily living activities , reduction in quality of life, loss of gainful employment, hopelessness and cognitive dysfunction. Recently, BMS has been defined as an EDSS score <2.0 after a disease duration of at least 10 years. 3 Over the past few years, BMS has been studied more systematically due to the current trend to treat patients early with disease-modifying therapies which would largely be unnecessary for benign patients. Recent research findings lead us to reconsider both the definition criteria and the frequency of truly BMS. In the literature, the estimated frequency of BMS varies from 6% to 64% of the whole MS population. 4 The two main factors accounting for this variability of estimates are differences in definition criteria and duration of the follow up. Indeed, when stringent criteria are used and observation is prolonged over time, the prevalence of BMS declines substantially both in population-based and clinic-based studies. 4 In a Canadian study that defined BMS as an EDSS ≤3.0 after at least 10 years, 169 BMS patients (representing approximately the 15% of the whole cohort of MS patients diagnosed between 1978 and 1984) were followed up for 20 years. Nearly 50% of these BMS subjects progressed to 'no longer benign status' by 20 years of observation, with more than 21% becoming severely disabled (EDSS ≥6.0). 5 This would result in a prevalence of BMS of nearly 7–8% after 20 years, using traditional criteria of definition that only rely on motor functioning. BMS therefore appears to represent just a temporary descriptor of the disease status rather than a permanent condition. Over the past few years, the results of accurate neu-ropsychological …