Previously, some glutamate receptor genes (N-methyl-D-aspartate [NMDA] receptor [NMDAR] subunits GRIN2A, GRIN2B; the kainate receptor subunits GRIK1, GRIK2, GRIK4, GRIK5; the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid [AMPA] receptor subunit GRIA1; and the metabotropic glutamate receptor GRM8) have been associated with MS disease severity (Baranzini et al., 2010, 2009; Strijbis et al., 2013; Wang et al., 2011). The gene discussed is GRIK5; the disease is myeloid sarcoma.