The report by Pulli et al ( 1 ) provides good preclinical evidence that MPO-Gd, a gadolinium-based magnetic resonance (MR) imaging probe for the enzyme myeloperoxidase (MPO), might be a more sensitive contrast agent for the detection of multiple sclerosis (MS) and may mark a pathologically specific proinflammatory component of the disease that might also provide the basis for novel therapies.