Neurogenetics and Multi-omics of Neuroinflammatory Diseases in Multiplex Families to Improve Patients Health

The goal of this observational study is to learn why some families have several members with multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), or MOG antibody-associated disease (MOGAD). These diseases happen when the immune system attacks the brain, optic nerves, or spinal cord. The study includes about 500 people from about 100 families: people with one of these diseases and their relatives who do not have it. The main question is: Do rare gene changes (variants) shared by family members explain why these diseases run in families? Researchers will compare the DNA of family members who have the disease with the DNA of relatives who do not. They will also look at how genes are switched on and off in blood cells. Participants will: * Attend one visit of 2 to 3 hours at one of five French hospitals * Answer questions about their health, treatments, and family history * Give a 50 mL blood sample