This contribution reports the case of a young female patient with a cytotoxic T-lymphocyte antigen 4 (CTLA-4) heterozygous missense mutation giving rise to a broad range of autoimmune diseases, including central nervous system inflammation presenting as disseminated intramedullary and infiltrating brain lesions on MRI. Multiple sclerosis was one of the diagnoses considered. CTLA-4 is a negative immune regulator essential for the function of regulatory T-cells, themselves responsible for maintaining self-tolerance and immune homeostasis. Heterozygous germline mutations in CTLA-4 may lead to an autosomal dominant immune dysregulation syndrome with highly variable phenotype, including various immunodeficiency and autoimmune diseases, along with neurological manifestations.