Moreover, complement components and regulators are elevated systemically and in the CSF of MS patients (Ingram et al., 2009; Ingram et al., 2010a, b; Ingram et al., 2012; Zelek et al., 2019) and early complement pathway gene variants (C3, C1QA, and CR1) have recently been associated with structural and functional measures of MS severity (Fitzgerald et al., 2019), indicating an inherent susceptibility to complement-mediated injury in some patients. The gene discussed is C3; the disease is myeloid sarcoma.