1. Department of Neurology, MS Centre ErasMS, Erasmus MC, Rotterdam, 3015 GD, the Netherlands
2. Departments of Epidemiology and Biostatistics, Genetic Epidemiology Unit, Erasmus MC, Rotterdam, 3015 GD, the Netherlands
3. Sanquin Blood Bank South West Region, Rotterdam, 3015 CN, the Netherlands
4. Clinical Genetics, Erasmus MC, Rotterdam, 3015 GD, the Netherlands