This study will identify a combination of disease severity markers (genetic, immunology, epigenetic, imaging) associated with disease severity and progression in a cohort of patients with multiple sclerosis.

The heterogeneity of multiple sclerosis evolution relies on several pathophysiological mechanisms including neuroinflammation, neurodegeneration and remyelination and repair mechanisms.

The study will identify markers of disease severity in a longitudinal cohort of patients with multiple sclerosis who are siblings (both siblings having multiple sclerosis) including: biological markers (genetic, immunological and epigenetic markers, advanced MRI markers). An integrative model to predict disease progression will be proposed based on multimodal markers.

Inclusion Criteria:

• Clinically isolated syndrome or Multiple sclerosis (2010 Mc Donald criteria)
• Sibling having Clinically isolated syndrome or Multiple sclerosis (2010 Mc Donald criteria) willing to participate to the study
• Affiliated to the French social security or equivalent

Exclusion Criteria:

• Cyclophosphamide, mitoxantrone or methylprednisolone infusion within one month before inclusion
• Multiple sclerosis relapse within one month before inclusion
• Concomitant severe or uncontrolled disease

Multiple Sclerosis siblings Group of siblings having multiple sclerosis, n=120