Environmental and Genetic Risk Factors for Pediatric Multiple Sclerosis

Children are eligible for this study as cases if: * They have MS or clinically isolated syndrome (CIS): * MS: As defined by the 2010 McDonald criteria for diagnosis of MS (Polman 2010), * CIS: A first demyelinating event indicating high risk for MS (i.e., one clinical event involving the spinal cord, the optic nerve, the brainstem or cerebellum, or occasionally the hemispheres) and at least 2 silent T2 bright areas on a brain or spinal cord MRI (at least one must be in the brain); AND * They are three years of age or older; AND * Disease onset occurred before 18 years of age. Patients are not eligible for study participation if: * Disease onset occurred more than 4 years prior to the opportunity to enroll; OR * They have had an organ transplant; OR * They are known to have neuromyelitis optica (NMO). Children are not eligible to participate as pediatric controls if: * They are two years of age or younger; OR * They are 22 years of age or older; OR * They are known to have MS or another demyelinating disease (for example, neuromyelitis optica or acute disseminated encephalomyelitis); OR * They have a biological family member who has been enrolled as a control; OR * They have an immediate, biological family member (parent/sibling) who has been diagnosed with MS; OR * They have an autoimmune disorder (except asthma or eczema); OR * They have had an organ transplant; OR * They have a chronic neurological condition with major disability (this does not include, for example, migraine, controlled seizures, and mild learning disabilities such as ADD or ADHD).