We concur with the comments of Lalive et al. regarding the limitations of our report on the first 15 cases of fingolimod-associated progressive multifocal leukoencephalopathy (PML).1 Duration of therapy and age appear to be important risk factors for the development of PML in association with fingolimod. In the article, we mentioned that “11 (73%) were women and the mean age was 53 years (median: 53 years). Fourteen of the 15 patients were treated with fingolimod for >2 years.”1 Although suggestive that age and duration of therapy may be associated with risk, the available data at the time of data lock precluded detailed statistical analysis, which explains our reluctance to report it. Despite additional cases having been reported, the number to date remains low with a high degree of uncertainty around the pattern of those associations and, in particular, around the existence of certain risk thresholds.