Patients who carry the HLA-DRB1*15:01 allele have shown positive correlation with oligoclonal bands (OCB) in CSF, early disease onset, risk of cognitive decline, presence of bigger white matter lesions, more advanced brain atrophy, higher lesion load on MRI, and higher concentration of matrix metalloproteinase-9 (MMP-9) in CSF [23,24]. This evidence concerns the gene MMP9 and Brain atrophy.