In MS (n = 19) compared with controls (n = 19), no difference in OD of CD200 was found when the whole GM was compared; however, there was a significantly lower OD of CD200 in Layers 1 and 2 (Layer 1 controls: 0.39 ± 0.07, MS: 0.35 ± 0.04, P = 0.03; Layer 2 controls: 0.41 ± 0.08, MS: 0.37 ± 0.04, P = 0.04). The gene discussed is CD200; the disease is myeloid sarcoma.