A natural history protocol for the evaluation of patients with genetically defined or undifferentiated pediatric diseases characterized by inflammation of the central nervous system using advanced genetics and immunophenotyping is currently being developed. Affected participants will be clinically evaluated and provide biological samples for research. Leftover samples from clinical procedures may also be used for research. Genotyping, HLA typing and immunophenotyping will be performed free of charge. Follow-up visit may be scheduled on the basis of clinical status, with the aim of molecularly characterizing biologic samples including CSF in both active and quiescent states. Unaffected biological parents will provide biological samples to be used as controls.