Investigators are going to recruit retrospectively all the patients treated with biotin since the product is available in France, in all French MS centers that agree to participate (maximum 30). They are going to collect through medical records, demographic data (as age, gender, MS center localization), but also data about the disease (as MS duration, primary progressive or secondary progressive MS), data about disability (with several Expanded Disability Status Scale -EDSS- scores at different time points) and data about treatments (as duration of biotin, existence of other concomitant disease-modifying therapy). For comparison, a control group without biotin is going also to be recruited from the European Database for Multiple Sclerosis (EDMUS). The same data as described above are going to be collected for the controls.
