Notably, three X chromosome candidate genes have been at the forefront of genetic association studies in MS: PLP (located on Xq22) (134), cytochrome b-245 β chain (CYBB or NOX2, Xp21) (263), and gamma-aminobutyric acid ionotropic type A receptor (GABRA3, Xq28) (135). This evidence concerns the gene CYBB and myeloid sarcoma.