The latter is commonly observed in multiple sclerosis (MS), where CTLA4 downregulation has also been reported, while certain polymorphic variants in CTLA4 are linked to reduced remyelination in MS, suggesting potential common underlying immunologic mechanisms between CTLA4 deficiency and ‘genuine’ MS [31,32,33,34,35,36]. The gene discussed is CTLA4; the disease is myeloid sarcoma.